Search

OBJECTIVE Tarlov cysts (TCs) are a common cystic entity in the sacral canal, with a reported prevalence between 1.5% and 13.2%; 10%–20% of patients are symptomatic and need appropriate clinical intervention. However, the choice of treatment remains controversial. The goal of this study was to describe a new microsurgical sealing technique for symptomatic sacral TCs (SSTCs) as well as its long-term outcomes. METHODS Microsurgical sealing was performed using a short incision, leakage coverage with a piece of autologous fat, and cyst sealing with fibrin glue. Postoperative data were collected at three stages: discharge, 1-year follow-up, and a follow-up of 3 years or more. According to the improvement in neurological deficits and degree of pain relief, outcomes were divided into four levels: excellent, good, unchanged, and deteriorated. RESULTS A total of 265 patients with SSTCs were treated with microsurgical sealing from January 2003 to December 2020. The mean follow-up was 44.69 months. The percentages of patients who benefited from the operation (excellent and good) at the three stages were 87.55%, 84.89%, and 80.73%, respectively, while those who received no benefit (unchanged and deteriorated) were 12.45%, 15.11%, and 19.27%, respectively. Of the patients with postoperative MRI, the cysts were reduced in size or disappeared in 209 patients (94.14%). CSF leakage from the wound was observed in 15 patients, and 4 patients experienced an infection at the incision. There were no cases of new-onset nerve injury or aseptic meningitis after the operation. CONCLUSIONS SSTC patients undergoing microsurgical sealing had persistently high rates of symptom relief and few postoperative complications. Microsurgical sealing is an effective, simple, and low-risk method for treating SSTCs.

Polypropylene (PP) and polyethylene (PE) play central roles in our daily life. However, their immiscibility presents a major hurdle in both industry and academia when recycling them into alloys with favorable mechanical properties. Moreover, typical compatibilizer-enabled approaches are limited due to increased environmental concerns. Herein, inspired by a traditional Chinese technique, we report a facile, industry-scale methodology that produces a PP/PE binary blend with a highly ordered honeycomb nanostructure without any additives. Due to its nanostructure, the blend exhibits enhanced tensile properties in comparison with the parent components or with a sample prepared using an internal mixer. This approach has potential for applications not only in immiscible polymer blending, but also in non-sorting, compatibilizer-free waste plastics recycling. Through this technique, we expect that an environmentally friendly and sustainable plastic wastes recycling avenue can be found, and great economic benefits can be gained.

Spinal cord injury (SCI) usually introduces permanent or long-lasting neurological impairments. Maintaining the integrity of limited number of white matter bundles (5–10%) preserves wholly or partially locomotor following SCI. Considering that the basic structure of white matter bundles is axon wrapped by oligodendrocytes, promoting oligodendrocytes survival might be a feasible strategy for reducing white matter injury (WMI) after SCI. Oligodendrocytes are rich in unsaturated fatty acid, and susceptible to ferroptosis-induced damage. Hence, exploring method to reduce ferroptosis is supposed to expedite oligodendrocytes survival, thereafter mitigating WMI to facilitate functional recovery post-SCI. Here, the results indicated the administration of hepcidin reduced iron accumulation to promote oligodendrocytes survival and to decrease spinal cord atrophy, thereafter facilitating functional recovery. Then, the WMI was evidently decreased due to attenuating ferroptosis. Subsequently, the results uncovered that the expression of divalent metal transporter 1 (DMT1) and transferrin receptor 1 (TfR1) was expressed in CC1+ cells. The expression level of DMT1 and TfR1 was significantly increased, while this phenomenon was obviously neutralized with the administration of hepcidin in the epicenter of spinal cord after SCI. Afterward, the application of hepcidin downregulated reactive oxygen species (ROS) overload, which was evidently increased with the treatment of 20 µM FeCl3, thereafter increasing cell viability and reducing lactate dehydrogenase (LDH) activity through downregulating the expression of DMT1 and TfR1 to inhibit ferroptosis in oligodendrocyte progenitor cells (OPCs). The present study provides evidence that the application of hepcidin expedites oligodendrocytes survival to alleviate WMI via minimizing the expression of DMT1 and TfR1.

The incorporation of high-dielectric permittivity ceramic or conductive fillers into the polymer is an effective method to obtain flexible high-performance dielectric materials, but it is still a huge challenge to achieve a balance between dielectric and mechanical properties. In this paper, we report a polyvinylidene fluoride (PVDF) nanocomposite based on a novel crab leg-like filler, in which Ag nanoparticles (AgNPs) were decorated on the surface of polydopamine (PDA)-coated silicon carbide (SiC) nanowhiskers (NWs). Compared with the nanocomposites with as-received SiC, this PVDF/SiC@PDA@Ag nanocomposites exhibited significantly suppressed dielectric loss (0.03 at 1 kHz) and leakage current. The Argant plot ( $${\varepsilon }^{^{\prime}}$$ - $${\varepsilon }^{\prime\prime}$$ curve) and electric modulus analysis demonstrated that the inhibition of the organic layer of PDA to interface polarization and the coulomb-blockade effect of AgNPs hindered carrier transport, which resulted in the largely suppressed dielectric loss. Furthermore, while the dielectric properties were improved, the PVDF/SiC@PDA@Ag nanocomposites also exhibited excellent mechanical and thermal conductivity. Ultimately, the nanocomposites prepared via this method are promising for applications in microelectronic devices.

Composite bipolar plates (BPs) are preferred to graphite BPs and metal BPs, in proton exchange membrane fuel cells (PEMFC), due to their pronounced advantages. However, facile and high-efficiency fabrication of high performance composite BPs, remains a challenge. In this study, high performance polyvinylidene fluoride (PVDF)/graphite/multi-walled carbon nanotubes (MWCNTs) composite BPs with segregated conductive network are prepared by structural design and compression molding. Due to the “brick-mud” structure formed in composite BPs by structural manipulation, its conductivity of low filler content is greatly improved. In addition, segregated synergistic conductive networks are observed in composite BPs after adding MWCNTs. The composite BP (5 wt% MWCNTs and 35 wt% graphite) exhibited electrical conductivity of 161.57 S/cm and area specific resistances of 7.5 mΩ cm2. Moreover, the composite BPs have good flexural strength, excellent hydrophobicity and corrosion resistance. In summary, our work provides a simple and feasible strategy for manufacturing high performance composite BPs with low fillers.

In this paper, the synthesized thermoplastic polyimide (TPI) precursor is coated on both surfaces of the surface-treated polyimide (PI) base film, and the TPI/PI/TPI multilayer films is obtained by thermal imidization. The mechanical properties, heat resistance, water absorption of the multilayer film and the interface between the TPI and the PI base film were investigated in detail. Then, multilayer film-2 (MF-2) with excellent comprehensive performance and the two copper foils were pressed together to prepare a double-sided flexible copper clad laminate (FCCL) by thermal lamination method, and the properties of FCCL were studied in detail. The results show that the FCCL has a high peel strength of 1.22 N/mm, passed a solder bath test of 288°C, and the surface condition was good under hot-pressing temperature of 360°C, hot-pressing pressure of 15 MPa and hot-pressing time of 60 s. In addition, the SEM and EDS spectra of the stripped copper foil confirmed that the TPI layer was immersed into the interstitial space of the Cu nodules, forming a strong physical bite with the copper foil. The current work provides a promising solution for the design and fabrication of multilayer printed circuit boards with excellent performance.

Thermal insulation polylactide (PLA) foams with high compressive strength were successfully fabricated by combining a modified cooling batch foaming method and introduction of stereocomplex (SC) cr...

In this study, a novel mixing device under convergent–divergent elongational flow is developed, mainly contains vane conveying unit and wedge channel unit, generating multi-source pulsating pressure in the mixing procedure to induce phase transition. During the design process, some mathematical works and simulations are conducted to optimize the structural design. High-density polyethylene (HDPE)/expanded graphite (EG) composites are fabricated by phase transition assisted melting mixing. The composites feature lower melt resistance and improved tensile modulus. Furtherly, the prepared HDPE/EG composites exhibit a greater increment of dielectric constant when adding more EG, but always maintain low dielectric loss about 0.05 in low frequency. These results show the excellent exfoliation and dispersion effect, confirming that this new designed equipment and phase transition effect complement each other with fabulous effect in the preparation of filler reinforced polymer.

Polylactide (PLA) microcellular foams with well-defined cell morphology were successfully fabricated from poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) blends through a supercritical carbon dioxide (CO₂) foaming method. The gaps between the melting temperature of homocrystallites (Tₘ₍HC₎) and stereocomplex crystallites (Tₘ₍SC₎) were utilized to improve PLA’s melt foaming behaviors (i.e., cell nucleation and cell morphology) owing to the existence of exclusive SC crystallites when the foaming temperature fell in between Tₘ₍HC₎ and Tₘ₍SC₎. Thanks to the enhanced melt strength, which resulted from the introduction of SC crystallites, the cell morphology transformed from elliptical to nearly circular and the cell collapse and coalescence reduced when foamed at high temperatures and pressures. The wider foaming processing window is favorable for actual industrial manufacture such as the continuous extrusion foaming process. In addition, PLA foams possessing more SC crystallites exhibit higher heat resistance, which further broadens their applications in high-temperature conditions.

Porous ultra-high-molecular-weight polyethylene (UHMWPE) self-lubricating materials were designed and fabricated by a rotary sintering method, and the microstructure and properties were evaluated. Results showed that the rotary molding could not only significantly improve the molding efficiency but also formed uniform internal microstructures with high porosity, excellent mechanical properties, and low friction coefficient. Under oil lubricating conditions, the friction curve of samples quickly reached a steady state, the friction coefficient was reduced by 50%, and the repeat utilization was up to 99%. The following optimum sintering conditions were shown: Sintering temperature of 180 &deg, C or 190 &deg, C, sintering time determined as 10 min, and loading capacity of between 3.6 g and 3.8 g. Therefore, it is expected that this work will open a convenient and compatible strategy for fabricating porous materials with good self-lubricating performance.

Inadequate decompressions can lead to poor improvement of symptoms in patients with Chiari I malformation (CMI). In this study, the “all-factors-surgery” that including all levels decompressions was performed on symptomatic CMI patients for the snake of eliminating all possible pathogenic factors and reducing the chance of reoperation. The “all-factors-surgery” combined operations of posterior fossa decompression, enlarged cranioplasty, duraplasty, cerebellar tonsil partial resection and adhesion release. Total 194 patients from January 2010 to December 2015. The outcome measures included improvement rate of symptoms, patients self-evaluation (improved, unchanged, worsened), Visual Analogue Scale (VAS) score, Japanese Orthopaedic Association (JOA) score, Chicago Chiari Outcome Scale (CCOS) score, the diameter of the syrinx and complications. Postoperative data were collected from the three stages: at discharge, the short-term follow-up (average, 9.39 months), and the long-term follow-up (average, 54.44 months). Patients self-evaluation improvement rate in the three follow-up stages was 92.27%, 90.07% and 85.93%. The VAS scores (mean, 1.49, 1.21, 1.47 vs 3.76) and JOA scores (mean, 15.66, 15.99, 16.10 vs 14.84) were significant difference between the follow-up and pre-operation (P

Ultra-high molecular weight polyethylene (UHMWPE)/carbon nanotubes (CNT) porous skeleton was prepared by microwave sintering, then paraffin wax (PW) was absorbed into UHMWPE/CNT porous skeleton by vacuum, obtaining composite phase change materials (CPCM). Differential scanning calorimetry (DSC) results showed that with CNT content of 1.5%, the PW adsorption of CPCM reached 59.91% and latent heat of the CPCM hardly changed after 20 melting/freezing cycles. Furthermore, thermal conductivity of porous matrix and CPCM from 0.1858 and 0.3012 W m − 1 K − 1 to 0.3272 and 0.4225 W m − 1 K − 1 with the CNT content increased (from 0% to 2%), respectively. In addition, the CPCM had a great shape stability. When the temperature reached 70 °C, PW in CPCM hardly leaked. In the photothermal conversion, CPCM realized the function of energy storage and release. Therefore, the CPCM prepared by a facile and environmentally friendly strategy with high energy storage efficiency, outstanding thermal repeatability, excellent thermal stability and high thermal conductivity had a broad prospect in the application of energy storage.

A synergic strategy combining chemical nucleation with chain extension was employed for Poly (ethylene terephthalate) (PET). In this study, sodium linoleate (Na-LL), as chemical nucleating agent, was selected to promote the nucleation process, and an ultraviolet-induced chain extension approach was simultaneously employed to maintain the molecular weight of PET with the aid of glycidyl methacrylate (GMA) / trimethylolpropane triacrylate (TMPTA). The rheological properties, crystallization behaviors and mechanical properties of PET composites were systematically explored. The rheological results showed that GMA/TMPTA blend is effective for PET chain extension reaction and the addition of Na-LL would not badly offset the chain extension effect of GMA/TMPTA. The non-isothermal and isothermal crystallization studies demonstrated that Na-LL is an effective organic nucleating agent for PET. Low loading of Na-LL can considerably improve the crystallization properties of PET. At last, the combination of GMA/TMPTA/Na-LL could also maintain the excellent comprehensive mechanical properties of PET.

Effects of unmodified halloysite nanotubes (HNTs) and hexadecyl trimethyl ammonnium bromide treated halloysite nanotubes (CTAB-HNTs) on the morphology as well as the thermal and rheological properties of the HNT-filled polypropylene (PP) composites were investigated. The composites were melt-blended with a novel vane mixer dominated by extensional deformation. Fourier transform infrared spectroscopy well demonstrated that ammonium molecules were successfully interacted with halloysite groups. Compared with unmodified HNTs, the modified HNTs had a better dispersion in the PP matrix. The degree of crystallinity increased with the introduction of HNTs into the PP matrix. Thermal analyses revealed that CTAB-HNTs can improve the composites’ thermal stability compared with unmodified HNTs. As for dynamic shear rheology, the PP/CTAB-HNT composites showed higher viscoelaticity than neat PP in most frequency regimes, and that the raw HNT/PP composites presented the opposite phenomenon. The relaxation time of PP melt and the availability of heterogeneous PP domains increased with the presence of CTAB-HNTs.

In this paper, long-chain branched polylactide (LCB-PLA) prepared by UV-induced reaction extrusion with trimethylolpropane triacrylate (TMPTA) was foamed by supercritical carbon dioxide (scCO2), and the effect of the long-chain branching structure on the cell morphologies of PLA foams was investigated. The LCB-PLA displayed higher complex viscosity, melting point and crystal nucleation potential under scCO2, and these factors could influence the foaming behavior of PLA which was proved by the different cell morphologies of samples foamed after various saturation times. The advantage of LCB-PLA on foaming was remarkable at high temperature and high pressure. LCB-PLA with more than 0.5% TMPTA showed nano-cells while the other samples showed micro-cells at 142 °C under 12 MPa, and the samples displayed elliptic cells with horizontal semimajor axis in linear PLA and circular cells or oval cells with vertical semimajor axis in LCB-PLA with increasing temperature. The improved cell morphology with reduced coalescence, no collapse and uniform cell distribution was also shown in LCB-PLA under higher pressure. All these results were due to the increasing matrix strength and higher crystal nucleation potential of LCB-PLA. The findings indicate that LCB-PLA possesses better foaming behavior at high temperature and high pressure. The wide foaming processing window of LCB-PLA would benefit the high temperature and high pressure foaming of PLA such as bead foaming and continuous extrusion foaming, thus broadening its application.

The introduction of long-chain branches (LCBs) in polypropylene (PP) during the extrusion process is normally induced by peroxide chemicals which are known to lead to the formation of secondary products in the resin. Here we report a novel synthesis method to prepare LCB-PP via in situ ozonolysis during reactive extrusion in the presence of a multifunctional agent. Depending on the fast ozonation of molten PP molecules, free radicals can be generated in PP macromolecules and induce chain scission reactions during extrusion. LCB structures of PP could be formed when a multifunctional agent, trimethylolpropane triacrylate (TMPTA), was added into the PP matrix during extrusion. The effect of reaction temperature, polymer flow rate and TMPTA concentration on the LCB-PP structures is discussed. Molecular parameters of LCB-PP were detected by MALS SEC technique. Various rheological plots including elongation rheological properties were applied to distinguish the LCB structures in PP samples. Without residues and by-products of peroxide in the final polymer resin, this synthesis method of LCB-PP has highly efficient and easily adjustable merits.

How to improve the accuracy of indoor positioning is a hot issue in the research of wireless indoor positioning technology. In order to solve the problem that Ultra Wideband (UWB) technology cannot locate accurately under the condition of non-line of sight (NLOS), this paper proposes an indoor positioning method combining UWB and Pedestrian Dead Reckoning (PDR).The method utilizes the advantages of high frequency noise characteristics of PDR to suppress the NLOS error generated by UWB. Furthermore, in order to get better integration of UWB and PDR, an improved square root unscented Kalman filter (ISR-UKF) is proposed. The simulation results show that the improved algorithm proposed in this paper can effectively improve the indoor positioning accuracy, and ensure the stability and continuity of the positioning system.

Various quantities of carbon fibers (CFs) (from 5% to 20% in weight) were added to matrix by melt blending to produce polylactic acid (PLA)/thermoplastic polyurethane (TPU)/CF composites. Differential scanning calorimetry measurements revealed that the CF content and mixing time had little influence on the crystallization and melting behavior of PLA. Thermogravimetric analysis showed that the introduction of CFs tended to decrease the thermal stability of PLA/TPU/CF composites, and the increase of mixing time tended to increase the thermal stability of PLA/TPU/CF composites when the mixing time is

The melting behavior and crystalline forms of isotactic polypropylene (iPP) samples crystallized under different conditions of pressure and temperature were investigated using differential scanning calorimeter (DSC) and wide-angle X-ray diffraction (WAXD), respectively. When treated with dynamic supercritical CO2(Sc-CO2), iPP samples undergo the formation of β-crystal that does not occur on the treatment with atmospheric pressure and static supercritical CO2(Sc-CO2) pressure. In addition, the relative content of β-crystal has deep dependence on melt state and depressurization rate. Depressurization plays very critical role in the formation of β-crystal by means of imposing three-dimensional tensile field during cell growth. The tensile field induced α-row nuclei where the formation of β-crystal occurred. This finding will provide one new method to induce β-crystal in iPP parts. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

Free-radical reactions of polymers, including biodegradable polymers via reactive extrusion, are normally induced by peroxide chemicals, which are known to lead to the formation of secondary products and impart some performances to the resin. Here, we report an ultraviolet (UV)-induced reactive extrusion, without employing a peroxide initiator, to control chain scission and branching reactions of polylactide (PLA). Through this technique, chain scission reaction of molten PLA induced by UV irradiation during extrusion was promoted to high-level efficiency. Degraded PLA samples had lower complex viscosity and storage modulus, because of random main chain scissions. Long-chain branched (LCB) structure of PLA was obtained when a multifunctional chemical agent, trimethylolpropane triacrylate (TMPTA), was added into the PLA matrix during extrusion. Various rheological plots including viscosity, storage modulus, loss tangent, and Cole–Cole plots were used to distinguish the LCB structures of PLA samples. Therma...

A simple approach to decorate multi-walled carbon nanotube (MWCNT)&ndash, reduced graphene oxide (RGO) hybrid nanoparticles with zinc oxide (ZnO) nanorods is developed to improve the electrical and mechanical properties of poly(vinyl chloride) (PVC)/MWCNT&ndash, RGO composites. The ZnO nanorods act as &ldquo, joint&rdquo, in three-dimensional (3D) MWCNT&ndash, RGO networks and the hybrid particles strongly interact with PVC chains via p-&pi, stacking, hydrogen bonds, and electrostatic interactions, which we confirmed by scanning electron microscopy (SEM) and Raman analysis. By introducing the ZnO nanorods, the RGO&ndash, ZnO&ndash, MWCNT hybrid particles increased 160% in capacitance compared with MWCNT&ndash, RGO hybrids. Moreover, the addition of RGO&ndash, MWCNT to PVC resulted in the mechanical properties of PVC being enhanced by 30.8% for tensile strength and 60.9% for Young&rsquo, s modulus at the loadings of 2.0 weight percent (wt.%) and 1.0 wt.%, respectively. Meanwhile, the electrical conductivity of PVC increased by 11 orders of magnitude, from 1 &times, 10&minus, 15 S/m to 1 &times, 4 S/m for MWCNT&ndash, RGO loading at 5.0 wt.%.

Poly(L-lactic acid) (PLLA) foams with unique nanocellular and needle-like morphology were successfully prepared by combining spherulite templating and supercritical carbon dioxide (CO2) foaming. The corresponding crystalline morphology formed under supercritical CO2 in PLLA was illustrated to investigate the foaming behavior of spherulites in detail. It was found that not only the degree of crystallinity but also the crystalline morphology played a vital role in cell nucleation and growth, thus the foam morphology. Nanocellular structure was primarily generated for the PLLA foamed at 100 °C and 12–24 MPa. Moreover, the morphological transition from approximate circular cells to needle-like cells occurred around 16 MPa at 100 °C because of the constraint of lamellae, and the two different structures coexisted at 100 °C and at pressures ranging from 16 to 24 MPa. The results indicated that the expansion ratio of spherulite was bigger than that of PLLA foam.

In this work, rapid ozone degradation of polypropylene (PP) was developed for the aim of rheology control using a reactive extrusion process. Experiments were carried out in a co-rotating intermeshed twin-screw extruder with varied polymer throughput and reaction temperature. Ozone was introduced into the extruder to rapidly oxidize molten PP in just several seconds period. The oxidized PP was characterized through melt flow index (MFI), rheological measurement, differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy tests. The influence of reactive temperature and polymer throughput on the degradation reaction was studied. It was noted that molten PP could be fast and successfully degraded during this reactive extrusion process. The oxidized PP had higher MFI than that of the origin PP resin, indicating the decrease of molecular weight of PP. Carbonyl groups were formed on the PP molecular chains. This rapid oxidization process has higher reaction efficiency than the ozone degradation of PP in solid state and no harmful byproduct would be generated from this ozonizing reaction.

In this work, design and development of a new melt mixing method and corresponding mixer for polymer materials were reported. Effects of ultrasonic power and sonication time on the carbon nanotubes (CNTs) filled ultra high molecular weight polyethylene (UHMWPE) nanocomposites were experimentally studied. Transmission Electron Microscopy images showed that homogeneous dispersion of CNTs in intractable UHMWPE matrix is successfully realized due to the synergetic effect of ultrasonic wave and extensional deformation without any aid of other additives or solvents. Differential scanning calorimetry results revealed an increase in crystallinity and crystallization rate due to the finer dispersion of the CNTs in the matrix which act as nucleating point. Composites' complex viscosity and storage modulus decreased sharply at first and then leveled off with the increase of sonication time or the ultrasonic power. The thermal stability and the tensile strength of the CNTs/UHMWPE nanocomposites improved by using this novel mixing method. This is the first method that combined the ultrasonic wave and the extensional deformation in which the elongation rate, sonication time and ultrasonic power can be adjusted simultaneously during mixing. The novel mixer offers several advantages such as environment-friendly, high mixing efficiency, self-cleaning and wide adaptability to materials.

This article proposes a novel extruder based on converging-diverging flow for polymer processing. The extruder is composed of four vane plasticizing and conveying units (VPCU) and three mixing units. The working principle of the new extruder is described in detail. Film was produced on this machine by using of CaCO3 filled LDPE composites. The film's mechanical properties were studied in terms of tensile strength and tear strength. The microstructure of the composites was studied in terms of SEM. The thermo-mechanical history of the material suffered in this extruder can be remarkably shortened in contrast to a single screw extruder with the same maximum output. Experimental results showed that the die pressure has little effect on output. More CaCO3 can be filled into the blend without degrading the parts performance.