Evolution of directly-spinnable carbon nanotube growth by recycling analysis

Carbon nanotubes (CNTs) grown on substrate-bound catalysts by CVD are influenced by the catalyst, which changes over the course of the process. The evolution of the CNT growth is revealed by breaking the process into recycling increments and using the phenomenon of ‘direct spinnability’ as a target characteristic.Using acetylene alone, it was found that the first four cycles gave 100% regrowth in height and mass yield of CNTs, with both properties falling to around 20% on the 5th cycle. A decrease in nanotube diameter was observed whilst the areal density increased. With the addition of hydrogen a 100% regrowth for the second cycle was observed, followed by a decrease to around 55%, 18% and 11% in both height and yield for subsequent cycles. The diameter increased, whilst the areal density decreased in subsequent cycles.In the absence of hydrogen the CNTs have around seven walls, decreasing to about three by the seventh cycle. With hydrogen, CNTs have five or six walls for all cycles. Raman spectroscopy indicates an increase in disorder in later cycles. Spinnability is high for initial cycles but drops sharply on the fourth cycle, or third cycle with hydrogen, as the nanotube forest tortuosity markedly increases.     

Preparation and characterization of chitosan films,crosslinked with symmetric aromatic dianhydrides to achieve enhanced thermal properties

This study has developed a new generation of crosslinked chitosan‐based films using symmetric aromatic dianhydrides as crosslinking agents. The formation of the dianhydride‐crosslinked chitosan hydrogel films was confirmed using Fourier transform infrared and solid‐state ¹³C NMR spectral analyses. The films obtained from these derivatives were characterized by their thermal, swelling and hydrophilic properties. The results showed that introducing a cyclic imide moiety into the chitosan matrices played a significant role in enhancing the thermal properties of these chitosan films. It was found that even at high levels of substitution, thermal stability of the studied chitosan derivatives was improved, in spite of a reduction in crystallinity. Heterocyclic imide linkages produced networks that were insoluble in both acidic and alkaline media but allowed swelling in aqueous media. An increase in the hydrophobicity of the chitosan film surfaces was observed after introduction of the cyclic imide moiety. These engineered films produced noteworthy results concerning their thermal and swelling properties. There is a need to further investigate these films for drug delivery and biomaterials applications. © 2014 Society of Chemical Industry     

Molecular Characterisation of Flavanone O-methylation in Eucalyptus

Flavonoids are ubiquitous polyphenolic compounds in plants, long recognised for their health-promoting properties in humans. Methylated flavonoids have received increasing attention due to the potential of methylation to enhance medicinal efficacy. Recently, Eucalyptus species with high levels of the O-methylated flavanone pinostrobin have been identified. Pinostrobin has potential commercial value due to its numerous pharmacological and functional food benefits. Little is known about the identity or mode of action of the enzymes involved in methylating flavanones. This study aimed to identify and characterise the methyltransferase(s) involved in the regiospecific methylation of pinostrobin in Eucalyptus and thereby add to our limited understanding of flavanone biosynthesis in plants. RNA-seq analysis of leaf tips enabled the isolation of a gene encoding a flavanone 7-O-methyltransferase (EnOMT1) in Eucalyptus. Biochemical characterisation of its in vitro activity revealed a range of substrates upon which EnOMT1 acts in a regiospecific manner. Comparison to a homologous sequence from a Eucalyptus species lacking O-methylated flavonoids identified critical catalytic amino acid residues within EnOMT1 responsible for its activity. This detailed molecular characterisation identified a methyltransferase responsible for chemical ornamentation of the core flavanone structure of pinocembrin and helps shed light on the mechanism of flavanone biosynthesis in Eucalyptus.     

Improving the tensile strength of carbon nanotube spun yarns using a modified spinning process

A modified process for the dry spinning of carbon nanotube (CNT) yarn is reported. The approach gives an improved structure of CNT bundles in the web drawn from the CNT forest and in the yarn produced from the twisted web leading to improved mechanical properties of the yarn. The process enables many different mechanical and physical treatments to be applied to the individual stages of the pure CNT spinning system, and may allow potential for the development of complex spinning processes such as polymer-CNT-based composite yarns. The tensile strength and yarn/web structure of yarn spun using this approach have been investigated and evaluated using standard tensile testing methods along with scanning electron microscopy. The experimental results show that the tensile properties were significantly improved. The effect of heat treatments and other yarn constructions on the tensile properties are also reported.     

MicroRNA Regulation of Breast Cancer Stemness

Recent advances in our understanding of breast cancer have demonstrated that cancer stem-like cells (CSCs, also known as tumor-initiating cell (TICs)) are central for progression and recurrence. CSCs are a small subpopulation of cells present in breast tumors that contribute to growth, metastasis, therapy resistance, and recurrence, leading to poor clinical outcome. Data have shown that cancer cells can gain characteristics of CSCs, or stemness, through alterations in key signaling pathways. The dysregulation of miRNA expression and signaling have been well-documented in cancer, and recent studies have shown that miRNAs are associated with breast cancer initiation, progression, and recurrence through regulating CSC characteristics. More specifically, miRNAs directly target central signaling nodes within pathways that can drive the formation, maintenance, and even inhibition of the CSC population. This review aims to summarize these research findings specifically in the context of breast cancer. This review also discusses miRNAs as biomarkers and promising clinical therapeutics, and presents a comprehensive summary of currently validated targets involved in CSC-specific signaling pathways in breast cancer.     

NMR spectroscopic and thermodynamic studies of the etherate and the α, α′, and γ phases of AlH3

Aluminum hydride (alane; AlH₃) has been identified as a leading hydrogen storage material by the US Department of Energy. With a high gravimetric hydrogen capacity of 10.1 wt.%, and a hydrogen density of 1.48 g/cm³, AlH₃ decomposes cleanly to its elements above 60 °C with no side reactions. This study explores in detail the thermodynamic and spectroscopic properties of AlH₃; in particular the α, α′ and γ polymorphs, of which α′-AlH₃ is reported for the first time, free from traces of other polymorphs or side products. Thermal analysis of α-, α′-, and γ-AlH₃ has been conducted, using DSC and TGA methods, and the results obtained compared with each other and with literature data. All three polymorphs were investigated by ¹H MAS-NMR spectroscopy for the first time, and their ²⁷Al MAS-NMR spectra were also measured and compared with literature values. AlH₃·nEt₂O has also been studied by ¹H and ²⁷Al MAS-NMR spectroscopy and DSC and TGA methods, and an accurate decomposition pathway has been established for this adduct.     

Histamine receptors in the isolated rat stomach fundus and rabbit aortic strips

The effects of histamine and 4-methylhistamine (a selective H2-agonist) were studied on the isolated rat stomach fundus and rabbit aortic strips superfused with Krebs' solution. The contraction induced by histamine was found to be mediated via mepyramine-sensitive H1, while the relaxation induced by the amine through metiamide-sensitive H2-receptors in both smooth muscles. Prior addition of metiamide to the superfusion medium caused an apparent dose-related potentiation in the response to histamine on the aortic strip but not on the stomach fundus strip. The relaxation produced by histamine on the aortic strip demonstrated when the muscle was pretreated with mepyramine and contracted by angiotensin II or serotonin. Metiamide competitively inhibited the relaxation induced by histamine but not by papaverine in both smooth muscles. 4-Methylhistamine produced only a relaxation in the rat stomach fundus which could be competitively inhibited by metiamide. This analog had no agonistic property in the aortic strip. From these results it was concluded that histamine H1-and H2-receptors are present in both smooth muscles. The predominant contractile effect of histamine is mediated through H1-receptors and the relaxing effect of the amine through H2-receptors.     

Vascular reaction following intramedullary nailing of the tibia in dogs

We have reinvestigated radioiodinated plasminogen as an agent for localizing preformed thrombi. Canine plasminogen was isolated from fresh plasma by the affinity chromatography technique on a lysine-sepharose 4B column and tagged with I-123 or I-131, at less than one iodine atom per molecule of enzyme, by the conventional ICI method. When injected into dogs more than 2 days after thrombus induction, radioiodinated plasminogen produced thrombus-to-blood activity ratios of 7.8 +/- 2.4. Thrombi as old as 6 days can be visualized in 80% of the cases. Both the weight of the thrombus and the thrombus-to-blood ratio are more variable for 1-day-old thrombi; this may be associated with plasminogen release accompanying thrombus retraction. The results suggest that radioiodinated plasminogen has potential as an imaging agent for pre-existing thrombi.     

Effect of a high-beef diet on the fecal bacterial flora of humans

Ten human volunteers completed a 4-month diet series consisting of 1 month each of a control diet, a meatless diet, a high-beef diet, and the same control diet. Fat and fiber contents were essentially the same in all four diets, but protein content was doubled during the high-beef diet. During the 4th week on each diet, three stool specimens collected from each volunteer were analyzed for chemical composition and content of facultative, aerobic, and anaerobic bacteria. The bacteriological data are presented in this paper. High beef protein consumption had little effect on the composition of the intestinal flora. There were no significant differences in total counts of facultative and aerobic or anaerobic organisms in the feces when volunteers were on meatless or high-beef diets. At the species level, when counts during the two control diets were comparable, in only three instances did the change from the meatless to a high-beef diet significantly influence the bacterial numbers. The ratio of mean counts of anaerobic to facultative and aerobic organisms was approximately 15:1 during the meatless diet and 34:1 during the high-meat diet. The data indicate that animal protein consumption has little effect on the fecal bacterial profile in humans.