Bidirectionally promoting assembly order for ultrastiff and highly thermally conductive graphene fibres.

Macroscopic fibres assembled from two-dimensional (2D) nanosheets are new and impressing type of fibre materials besides those from one-dimensional (1D) polymers, such as graphene fibres. However, the preparation and property-enhancing technologies of these fibres follow those from 1D polymers by improving the orientation along the fibre axis, leading to non-optimized microstructures and low integrated performances. Here, we show a concept of bidirectionally promoting the assembly order, making graphene fibres achieve synergistically improved mechanical and thermal properties. Concentric arrangement of graphene oxide sheets in the cross-section and alignment along fibre axis are realized by multiple shear-flow fields, which bidirectionally promotes the sheet-order of graphene sheets in solid fibres, generates densified and crystalline graphitic structures, and produces graphene fibres with ultrahigh modulus (901 GPa) and thermal conductivity (1660 W m-1 K-1). We believe that the concept would enhance both scientific and technological cognition of the assembly process of 2D nanosheets.

Falling-Leaves Stacking Aggregation of Two-Dimensional Macromolecular Graphene Oxide in Solution.

Understanding the dynamical behaviors of two-dimensional (2D) macromolecules is of fundamental importance for the precise modulation of their assembled structures and material performances. However, considerably less is known about how discrete macromolecular sheets aggregate into extended macroscopic assemblies in solutions. The absence of a quantitative description of the assembly process limits the precise structural control of assemblies. Here, we investigated the aggregation thermodynamic transition and kinetic behavior of 2D macromolecules in the model of single layer graphene oxide (GO). Combining Flory-Huggins theory with experimental observations, we unveiled the critical thermodynamic transition of GO to correlate with the solvent property. We proposed a theoretical falling-leaf model to quantitatively describe the kinetic aggregation process of 2D GO sheets. Experimental analysis validated the theoretical prediction that the thickness of GO aggregates has a power law relation with the poor solvent content. Our work provides a fundamental understanding of phase separation of 2D macromolecules and offers an insight into modulating the aggregated structures of their assembled materials.

Superior Strong and Tough Nacre-Inspired Materials by Interlayer Entanglement.

Natural materials teach that mechanical dissipative interactions relieve the conflict between strength and toughness and enable fabrication of strong yet tough artificial materials. Replicating natural nacre structure has yielded rich biomimetic materials; however, stronger interlayer dissipation still waits to be exploited to extend the performance limits of artificial nacre materials. Here, we introduce strong entanglement as a new artificial interlayer dissipative mechanism and fabricate entangled nacre materials with superior strength and toughness, across molecular to nanoscale nacre structures. The entangled graphene nacre fibers achieved high strength of 1.2 GPa and toughness of 47 MJ/m3, and films reached 1.5 GPa and 25 MJ/m3. Experiments and simulations reveal that strong entanglement can effectively dissipate interlayer energy to relieve the conflict between strength and toughness, acting as natural folded proteins. The strong interlayer entanglement opens up a new path for designing stronger and tougher artificial materials to mimic but surpass natural materials.

A reproducible model of intramedullary spinal cord tumor in rats bearing RG2 cells.

Intramedullary spinal cord tumors (IMSCTs) are lethal diseases to many patients. The lack of adequate animal model has hampered the development of novel treatments. In the current study, a rodent intramedullary glioma model is established to study IMSCT progression. Fischer 344 rats received a intramedullary implantation of RG2 glioma cells. The neurological state of each rat was evaluated on daily basis using the Basso, Beattie and Bresnahan (BBB) scale. Rats implanted with RG2 cells developed significant hind limb paraplegia 20 days after implantation. Magnetic resonance imaging (MRI) scans after three weeks revealed significant intramedullary RG2 tumors in the rats. Forty days post implantation, rats were sacrificed for histopathological examination. Neuro-imaging and HE staining cross sections confirmed intramedullary RG2 glioma cells invading to the spinal cord. Thus, our model displayed many of the same invasive characteristics as human IMSCTs. This model should be a reliable and reproducible methodology to correlate well with the features of human IMSCT.

Novel combination of paraspinal keyhole surgery with a tubular retractor system leads to significant improvements in lumbar intraspinal extramedullary schwannomas.

The aim of the present study was to investigate the efficacy of combining paraspinal keyhole surgery with a tubular retractor system for the microsurgical removal of lumbar intraspinal extramedullary schwannomas. A retrospective analysis was conducted of 56 patients with lumbar intraspinal extramedullary schwannomas who were treated using the microsurgical paraspinal keyhole approach with a tubular retractor system. The mean ± standard deviation was calculated for the following parameters: Surgery time (96.21±14.64 min), hemorrhagic volume (28.54±9.72 ml), bed rest (2.55±0.5 days) and hospital stay (5.68±0.72 days). Two patients presented with cerebrospinal fluid leakage and one patient exhibited a nerve root injury. At a 6-month follow-up visit, postoperative Japanese Orthopedic Association (JOA) and visual analog scale (VAS) scores were evaluated. The mean ± standard deviation JOA scores were 12.00±2.07 for preoperative, 14.73±2.05 for 1 week postoperative, 20.07±2.32 for 3 months postoperative and 21.75±2.18 for 6 months postoperative. The improvement rate was 16.07, 47.48 and 59.77%, respectively. The mean ± standard deviation VAS scores were 6.64±1.31 for preoperative, 3.82±1.51 for 1 week postoperative, 2.11±1.17 for 3 months postoperative and 1.50±1.51 for 6 months postoperative. The JOA and VAS scores improved significantly (P<0.05). Magnetic resonance imaging and computed tomography were performed preoperatively, immediately following surgery and at the 6-month postoperative visit to confirm the efficacy of the resections and evaluate spinal stability. No residual tumors were identified at follow-up. No alterations in the stability of the spine were observed postoperatively. The combination of the microsurgical paraspinal keyhole approach with the tubular retractor system was successful in treating lumbar intraspinal extramedullary schwannomas. The surgical approach was associated with decreased hemorrhages, decreased duration of hospital stay, faster recovery and improved postoperative maintenance of spinal stability.

Spontaneous spinal epidural hematoma management with minimally invasive surgery through tubular retractors: A case report and review of the literature.

To report a minimally invasive paraspinal approach in the treatment of a case of spontaneous spinal epidural hematoma (SSEH). We additionally aim to review the relevant literature to enhance our knowledge of this disease. SSEH is an uncommon but potentially catastrophic disease. Currently, most appropriate management is emergence decompression laminectomy and hematoma evacuation. An 81-year-old woman was admitted to the neurology department with a chief complaint of bilateral numbness and weakness of the lower limbs and difficulty walking for 4 days with progressive weakness developed over the following 3 days accompanied with pain in the lower limbs and lower back. No history of trauma was reported. Magnetic resonance imaging of the thoracolumbar spine demonstrated an epidural hematoma extending from T-12 to L-5 with thecal sac and cauda equina displacement anterior. The patient was treated in our department with a minimally invasive approach. This operation method had been approved by Chinese Independent Ethics Committee. Three months following the operation, the patient had regained the ability to walk with the aid of a cane and myodynamia tests revealed normal results for the left lower limb and a 4/5 grade for the right limb. Importantly, no complications were exhibited from the surgical operation. The minimally invasive paraspinal approach through tubular retractors is demonstrated here as an effective alternative method for the treatment of SSEH.

Poly(N-acylethylenimine) copolymers containing pendant pentamethyldisiloxanyl groups. I. Synthesis.

10-(Pentamethyl disiloxanyl) decyl oxazoline (Si) was synthesized. It was copolymerized with either undecyl (U) or nonyl (N) oxazolines using methyl 4-nitrobenzenesulfonate as initiator. Two series of random poly(N-acylethylenimine) copolymers, U/Si and N/Si, were synthesized over the whole composition range of Si monomer with a total degree of polymerization of about 100. Narrow molecular weight distributions were obtained. At a monomer to initator ratio of about 1060, the final degree of polymerization was 374 with a polydispersity index of 1.93. This shows the effect of chain transfer in this system.