A series of electron-deficient 1-hydroxy-2,3,5,6,7-pentaalkoxyanthra-9,10-quinones has been synthesized. All nine members of the series were found to be liquid crystalline, forming columnar mesophases over a broad temperature range. Such supramolecular building blocks can be used for the preparation of novel discotic dimers, oligomers, polymers and metallomesogens. 相似文献
Sum-frequency-generation (SFG) vibration spectroscopy is a technique only sensitive to functional groups arranged without centrosymmetry. For crystalline cellulose, SFG can detect the C6H2 and intra-chain hydrogen-bonded OH groups in the crystal. The geometries of these groups are sensitive to the hydrogen bonding network that stabilizes each cellulose polymorph. Therefore, SFG can distinguish cellulose polymorphs (Iβ, II, IIII and IIIII) which have different conformations of the exocyclic hydroxymethylene group or directionalities of glucan chains. The C6H2 asymmetric stretching peaks at 2,944 cm?1 for cellulose Iβ and 2,960 cm?1 for cellulose II, IIII and IIIII corresponds to the trans-gauche (tg) and gauche-trans (gt) conformation, respectively. The SFG intensity of the stretch peak of intra-chain hydrogen-bonded O–H group implies that the chain arrangement in cellulose crystal is parallel in Iβ and IIII, and antiparallel in II and IIIII. 相似文献
Recently, it has been shown that by using a single‐site catalytic system having titanium as a metallic center, it is possible to tailor the entanglement density in the amorphous region of a semi‐crystalline ultra‐high molecular weight polyethylene (UHMWPE). This route provides the possibility to make high‐modulus, high‐strength uniaxially and biaxially drawn tapes and films, without using any solvent during processing. In this publication, it is shown that a single‐site catalyst having chromium as metallic center, proposed by Enders and co‐workers, can also be tuned to provide control on the entanglement density during synthesis of the UHMWPE. However, to achieve the goal some modifications during the synthesis are required. The synthesized polymers can be processed in the solid state below the equilibrium melting temperature, resulting in uniaxially drawn tapes having tensile strength and modulus greater than 3.5 N/tex and 200 N/tex, respectively. Rheological studies have been performed to follow the increase in entanglement density in melt state with time.
Chelating resins based on biopolymers, specifically cellulose, offers a green analytical method for determination of metal ions at trace levels present in various samples. It offers a fast, accurate and simple method for separation and pre-concentration of metal ions at low concentrations, prior to their determination by instrumental method. Cellulose based chelating resin (CELL-GLY) has been synthesised by immobilising glycine on it. CELL-GLY was used for the determination of trace amounts of Cu2+ and Ni2+ from aqueous solutions before their determination by FAAS. The preparation of CELL-GLY involves simple steps, based on natural and easily available biopolymer cellulose, which makes its use as chelating resin is a green method. The Cu2+ and Ni2+ can be quantitatively recovered from the CELL-GLY in the pH range 4.8–6.9 and 6.9-7.8 respectively with a recovery of more than 95% for each of these metal ions. Recovery of these metal ions using CELL-GLY was quantitative up to 35 °C. The detection limits for copper and nickel by FAAS were 1.20 ppb and 1.40 ppb, respectively. The method was successfully employed for the determination of trace amounts of Cu2+ and Ni2+ in various samples. 相似文献
Journal of Radioanalytical and Nuclear Chemistry - Efficient and selective extraction of 137Cs and 90Sr from high level liquid waste (HLLW) is of utmost importance in the back end nuclear fuel... 相似文献
The muscle metabolism of at-rest patients with varying degrees of postpolio residual paralysis (PPRP) was studied and compared with that of controls using in vivo phosphorus magnetic resonance spectroscopy. The phosphocreatine (PCr)/inorganic phosphate (Pi) and PCr/adenosine triphosphate ratios were lower in patients than in controls. Reduction in PCr/Pi suggests abnormalities in oxidative phosphorylation. A significant increase was observed in the phosphomonoester/PCr ratio in patients, indicating the accumulation of intermediary compounds of the glycolytic pathway. Furthermore, the phosphodiester/PCr ratio was also significantly increased in patients. In general, the observed changes in metabolite ratios were found to be related to the degree of residual paralysis, suggesting that metabolic changes are secondary to chronic neurogenic processes. These metabolic alterations appear to be the possible cause of energy deficit and underlying muscle fatigue in PPRP patients. The present results provide an insight into the metabolic impairment and degree of muscle damage in patients with PPRP. 相似文献
In this paper, we have described a simple hydrothermal method for preparation of fluorescent carbon dots (C-dots) using Carica papaya juice as a precursor. The synthesized C-dots show emission peak at 461 nm with a quantum yield of 7.0 %. The biocompatible nature of C-dots was confirmed by a cytotoxicity assay on E. coli. The C-dots were used as fluorescent probes for imaging of bacterial (Bacillus subtilis) and fungal (Aspergillus aculeatus) cells and emitted green and red colors under different excitation wavelengths, which indicates that the C-dots can be used as a promising material for cell imaging. 相似文献
Specific immune detection of glycated hemoglobin is still a great challenge owing to the small epitopic difference between Hemoglobin (Hb) and HbA1c. We report a new electrochemical immunoassay format for point of care testing of HbA1c. A conducting self‐assembled monolayer of mercaptophenyl boronic acid (MPBA) was used as a capture layer for binding of glycated proteins and ferrocene tagged anti‐HbA1c antibody (FcAb) as a tracer molecule on a gold screen printed electrode. Validation of the new HbA1c assay was carried out using 6 clinical samples with known HPLC values and a correlation coefficient of 98 % was observed. 相似文献
Abstract An efficient protocol for the stereoselective synthesis of pyrazolo[5,1-b]thiazole-3-carboxylate tethered β-lactam conjugates 8a–j from novel pyrazolo [5,1-b]thiazole-3-carboxylate substituted Schiff’s bases 6a–f is reported here. The reaction between various ketene precursors and novel Schiff’s bases 6a–f afforded exclusive formation of trans-β-lactams 8a–j. The substrate scope of this approach was investigated extensively by varying different groups (R, Z). All the novel compounds were characterized using various spectroscopic techniques, such as FT-IR, 1H NMR, 13C NMR, elemental analysis, 13C NMR (DEPT-135), and mass spectrometry in representative cases. Single crystal X-ray crystallographic study of trans-ethyl 7-(1-(4-methoxyphenyl)-4-oxo-3-phenoxyazetidin-2-yl)-6-methyl-2-(methylthio)pyrazolo[5,1-b]thiazole-3-carboxylate 8a has confirmed the molecular structure and the stereochemical outcome. To the best of our knowledge, the synthesis of such types of Schiff’s bases and β-lactam conjugates has not been reported so far. 相似文献