Preparation,optimization and swelling study of carboxymethyl sago starch (CMSS)–acid hydrogel

In this study, sago starch was modified in order to enhance its physicochemical properties. Carboxymethylation was used to introduce a carboxymethyl group into a starch compound. The carboxymethyl sago starch (CMSS) was used to prepare smart hydrogel by adding acetic acid into the CMSS powder as the crosslinking agent. The degree of substitution of the CMSS obtained was 0.6410. The optimization was based on the gel content and degree of swelling of the hydrogel. In this research, four parameters were studied in order to optimize the formation of CMSS–acid hydrogel. The parameters were; CMSS concentration, acetic acid concentration, reaction time and reaction temperature. From the data analyzed, 76.69% of optimum gel content was obtained with 33.77 g/g of degree of swelling. Other than that, the swelling properties of CMSS–acid hydrogel in different media such as salt solution, different pH of phosphate buffer saline solution as well as acidic and alkaline solution were also investigated. The results showed that the CMSS–acid hydrogel swelled in both alkaline and salt solution, while in acidic or low pH solution, it tended to shrink and deswell. The production of the hydrogel as a smart material offers a lot of auspicious benefits in the future especially related to swelling behaviour and properties of the hydrogel in different types of media.     

Beam optics studies for the planned hybrid electrostatic-magnetic guided slow positron beam in Hong Kong

Design simulations are presented of a variable energy (0–40 keV) slow-positron beam that incorporates the convenience of magnetic guidance with the desirability of some electrostatic focusing produced by a lens structure operating in a low but increasing magnetic field region. Filtering of unmoderated positrons and gamma rays is to be accomplished using two conventionalE×B filters. In a novel way it is proposed that the final beam energy be adjusted using a simple linear de-acceleration stage and that the optimal electrostatic element potentials for efficient extraction, focusing and filtering of positrons be floated relative to the de-acceleration potential. The resulting intense and easily controllable sub-millimetre diameter beam should be suitable for both lateral and depth profiling of defects in semiconductor materials.Paper presented at the 132nd WE-Heraeus-Seminar on Positron Studies of Semiconductor Defects, Halle, Germany, 29 August to 2 September 1994     

Capillary electrophoresis for determination of free and albumin-bound bilirubin and the investigation of drug interaction with bilirubin-bound albumin

Capillary electrophoresis (CE) is a promising technique for assessment of free bilirubin and its interaction with albumin, as it requires only a small sample volume and provides a rapid and efficient separation of free bilirubin from its albumin-bound complex in a one-phase system. In order to maintain the equilibrium without dissociation of bilirubin from the albumin/bilirubin complex as in real clinical conditions, the coupling of CE with frontal analysis (FA) was investigated. A very large sample plug was introduced hydrodynamically into the capillary (36 cm length, 50 microm inner diameter) at 15 psi x s to develop the frontal conditions during CE separation. The working conditions for CE/FA separation of bilirubin and albumin were optimized as follows: +20 kV; running buffer, 10 mmol/L phosphate and 1 mmol/L ethylenediaminetetraacetic acid (EDTA), pH 7.4. The working range for bilirubin was found to vary from 5 to 206 micromol/L; precision with relative standard deviation (RSD) <2.0% for n = 3 and detection limit (signal to noise, S/N = 2) was 2 micromol/L. The residual binding capacity of a simulated cord blood serum for bilirubin was 26 mg/100 mL at pH 7.4. Bilirubin was shown to be displaced from albumin when aspirin was added. The free bilirubin concentration was found to increase to clinical significant concentrations from 11.9 to 21.1% when increasing aspirin was added in the range of 5-50 mg/100 mL, respectively. Thus, the investigation of aspirin displacement of bilirubin from albumin is clinically important and the CE/ FA method is a suitable procedure for this purpose.     

Genotyping the -6A/G functional polymorphism in the core promoter region of angiotensinogen gene by microchip electrophoresis

Angiotensinogen (AGT) gene has been regarded as one of the candidate genes for essential hypertension. In our study, the role of AGT gene as a putatively predisposing gene for hypertension was evaluated by genotyping a A (-6) G polymorphism in the core promoter region in 123 patients with essential hypertension and 103 healthy controls. A microchip electrophoresis method coupled with polymorphism chain reaction (PCR)-restriction fragment length polymorphism (RFLP) assay was used for genotyping the A (-6) G single-nucleotide polymorphism. The separation and detection of the digested PCR amplicons were completed just in 280 s or less. The genotype frequency fulfilled the criteria of the Hardy-Weinbery equilibrium (X2 = 3.067, P > 0.05). The results showed a higher frequency of the -6 A allele (0.70) in the normotensive subjects, which is higher than those reported in Germany (0.47) and Czech (0.40) populations, but similar to that found in Japanese populations (0.73). The frequencies of genotype AA, AG, and GG were 0.46, 0.49, and 0.05 in hypertensive subjects, and 0.44, 0.53, and 0.03 in control subjects. There is no significant difference in the distributions of the genotype and allele between the two groups (X2 = 0.88, P > 0.05; X2 = 0.024, P > 0.05). These findings differ from some of the results obtained in other ethnic groups, indicating the potential importance of ethnic origin in the assessment of genetic risk identifiers for a complex disease.     

Luminescence Behavior of Polynuclear Alkynylcopper(I) Phosphines

A series of soluble trinuclear and tetranuclear copper(I) complexes containing ₃-^l acetylides , and have been synthesized and shown to exhibit rich photoluminescent behavior at room temperature. The electrochemistry of the trinuclear Cu(I) acetylide complexes and the excited-state redox properties of have been investigated. The X-ray crystal structures of and have been determined.