Metastases to the craniovertebral junction: illustrative case report and review of literature

Metastases at the craniovertebral junction represent 0.5-1% of spinal metastatic lesions. Common primary sites include breast, lung and prostate carcinoma. Initial presenting features include neck pain and occipital neuralgia. High index of suspicion is required to recognize this entity in patients presenting with neck pain. If left unrecognized, these metastatic lesions have the propensity to cause catastrophic collapse leading to significant morbidity and mortality due to fracture subluxation and spinal cord compression. Here we discuss such a patient who presented with acute onset quadriparesis and lower cranial nerve palsies due to metastatic lesion involving the C1 and C2 vertebra causing medullary and cervical cord compression. Early detection and timely intervention are key to improving outcomes in such patients

Metastases to the craniovertebral junction: illustrative case report and review of literature

Metastases at the craniovertebral junction represent 0.5-1% of spinal metastatic lesions. Common primary sites include breast, lung and prostate carcinoma. Initial presenting features include neck pain and occipital neuralgia. High index of suspicion is required to recognize this entity in patients presenting with neck pain. If left unrecognized, these metastatic lesions have the propensity to cause catastrophic collapse leading to significant morbidity and mortality due to fracture subluxation and spinal cord compression. Here we discuss such a patient who presented with acute onset quadriparesis and lower cranial nerve palsies due to metastatic lesion involving the C1 and C2 vertebra causing medullary and cervical cord compression. Early detection and timely intervention are key to improving outcomes in such patients

Stabilization of γ-sterilized biomedical polyolefins by synergistic mixtures of oligomeric stabilizers. Part II. Polypropylene matrix

In our previous study we have found the synergistic combinations of stabilizers which follow different mechanisms of stabilization and are approved for food contact and biomedical applications. The present attempt is to test the potentials of those systems in stabilizing γ-sterilized isotactic polypropylene (i-PP). Isotactic polypropylene was melt-mixed with hindered amine stabilizers (HAS), phenolic antioxidants and organo-phosphites (hydroperoxide decomposer) and sterilized with different doses of γ-radiation. Stabilization was monitored in terms of changes in the functional groups (oxidation products), tensile properties, yellowing and surface morphology by FTIR spectroscopy, Instron, colorimetry (reflectance) and scanning electron microscopy (SEM), respectively. The trend in stabilizing the efficiency of binary (1:1), ternary (1:1:1) and quaternary (1:1:1:1) additive systems was confirmed by comparing the stabilizing efficiency of mixtures with and without phenol system as well as with their counter parts of EP copolymer matrix. The binary system of secondary HAS and tertiary HAS, has shown antagonistic effect of stabilization whereas their combination with organo-phosphite has exhibited synergistic effect even at higher doses of γ-sterilization. Due to the oxidation of hindered phenol, phenol systems have shown discoloration and it was reduced by mixing with secondary HAS, tertiary HAS and organo-phosphite. The response of the stabilizer systems is better to ethylene-propylene (EP) copolymer than to i-PP in terms of stabilization

Effect of γ-dose rate on crystallinity and morphological changes of γ-sterilized biomedical polypropylene

The present work is aimed to study the changes in crystallinity and morphology of biomedical polyolefins after γ-sterilization. The isotactic polypropylene (iPP) films were sterilized by γ-radiation and the changes were characterized by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and atomic force microscopy (AFM) techniques. The effect of dose rate on crystallinity changes also was focused. It was found that crystallinity and morphology significantly changed with γ-irradiation. There was an increase in crystallinity up to 10 kGy accompanied with decrease in viscosity and mechanical properties. The changes in crystallinity mainly depend on γ-irradiation dose and dose rate. The rise in crystallinity was attributed to chain scission and forming new perfect lamellae. However, the reduction was accompanied by occurrence of γ- and β-phases and crosslinking. Possible explanations for transitions in phases are also discussed based on our results

Stabilization of γ-sterilized biomedical polyolefins by synergistic mixtures of oligomeric stabilizers

The stabilization of polyolefins against γ-sterilization has been studied with single or binary additive system. The present attempt is to utilize synergistic mixtures of stabilizers which are approved for food contact applications. Ethylene-propylene (EP) copolymer has been melt-mixed with hindered amine stabilizers (HAS), phenolic antioxidants and organo-phosphites (hydroperoxide decomposer). Samples were sterilized with different doses of γ-radiation. Stabilization was characterized in terms of changes in the functional groups (oxidation products), tensile properties, yellowing and surface morphology by FTIR spectroscopy, Instron, colorimetry (reflectance) and scanning electron microscopy (SEM), respectively. Results were discussed by comparing the stabilizing efficiency of mixtures with and without phenol system. Among phenol containing systems, where we mostly observe discoloration due to the oxidation of hindered phenol and the combination of secondary HAS, tertiary HAS, organo-phosphite and hindered phenol exhibited improved stabilization efficiency than single or binary additive systems. The mixture of secondary HAS and tertiary HAS, has shown antagonistic effect of stabilization whereas their combination with organo-phosphite has exhibited synergistic effect of stabilization even at higher doses of γ-sterilization. The effects have been explained through the interaction between the stabilizers

Effect of pressboard ageing on power transformer mechanical vibration characteristics

Power transformer winding clamping pressure is a critical parameter, which is directly related to transformer short circuit ride through capability. Mechanical impacts generated on the winding structure during short circuit faults, switching surges and other high current faults have a significant impact on the winding clamping structure and could lead to reduce the clamping pressure. The change in clamping pressure influences the vibration behaviour of winding structure. Hence, variations in clamping pressure can be assessed by monitoring the transformer vibrations. However, it has been observed that, not only progressive loss of clamping pressure but also solid insulation ageing has a significant influence on the winding vibration characteristics. Therefore, for a proper analysis of transformer vibration a clear understanding of the effect of solid insulation ageing on vibration behaviour of transformer winding structure is essential. This study aims to investigate the sensitivity of the transformer winding vibration characteristics to ageing of solid insulation material. Variations in modal parameters of winding structure with solid insulation ageing is studied using Finite Element Modelling (FEM). Results are used to discuss the sensitivity of winding vibrations to solid insulation ageing

Spinifex nanocellulose derived hard carbon anodes for high-performance sodium-ion batteries

The selection of an appropriate anode material is a critical factor in dictating the effectiveness of sodium-ion batteries as a cost-effect alternative to lithium-ion batteries. Hard carbon materials sourced from biomass offer the potential for a more sustainable anode material, while also addressing some of the thermodynamic issues associated with using traditional graphite anodes for sodium-ion batteries (NIBs). Herein, we report the preparation of carbon electrode materials from low-cost cellulose nanofibers derived from an Australian native arid grass 'spinifex' (Triodia pungens). This nanocellulose derived carbon produced by a fast, low temperature carbonization protocol showed superior performance as an anode for NIBs with a specific capacity (386 mA h g-1 at 20 mA g-1) on par with that of the graphite based anode for lithium-ion batteries, and is one of the highest capacity carbon anodes reported for NIBs. The excellent electrochemical performance is attributed to the large interlayer spacing of the carbon (∼0.39 nm). Superior cycling stability and high rate tolerance (326 mA h g-1 at 50 mA g-1 and 300 mA h g-1 at 100 mA g-1) suggest that hard carbons derived from sustainable precursors are promising for next generation rechargeable batteries.</p

Water-responsive mechanically adaptive nanocomposites based on styrene-butadiene rubber and cellulose nanocrystals - processing matters

Biomimetic, stimuli-responsive polymer nanocomposites based on a hydrophobic styrene-butadiene rubber (SBR) matrix and rigid, rod-like cellulose nanocrystals (CNCs) isolated from cotton were prepared by three different approaches, and their properties were studied and related to the composition, processing history, and exposure to water as a stimulus. The first processing approach involved mixing an aqueous SBR latex with aqueous CNC dispersions, and films were subsequently formed by solution-casting. The second method utilized the first protocol, but films were additionally compression-molded. The third method involved the formation of a CNC organogel via a solvent exchange with acetone, followed by infusing this gel, in which the CNCs form a percolating network with solutions of SBR in tetrahydrofuran. The thermomechanical properties of the materials were established by dynamic mechanical thermal analysis (DMTA). In the dry state, all nanocomposites show much higher tensile storage moduli, E′, than the neat SBR or the SBR latex. E′ increases with the CNC content and depends strongly on the processing method, which appears to influence the morphology of the SBR nanocomposites produced. The highest E′ values were observed for the solution cast samples involving an SBR latex, where E′ increased from 3 MPa for the neat SBR to ca. 740 MPa for the nanocomposite containing 20% v/v CNCs. Upon submersion in deionized water, a dramatic reduction of E′ was observed, for example from 740 to 5 MPa for the solution-cast nanocomposite containing 20% v/v CNCs. This change is interpreted as a disengagement of the percolating CNC network, on account of modest aqueous swelling and competitive hydrogen bonding of water molecules with the CNCs. It is shown that the method of preparation also influenced the swelling behavior and kinetics of modulus switching, consistent with different arrangements of the CNCs, which serve as channels for water absorption and transport within the hydrophobic SBR matrix