A Structural Study of Epoxidized Natural Rubber (ENR-50) and Its Cyclic Dithiocarbonate Derivative Using NMR Spectroscopy Techniques

A structural study of epoxidized natural rubber (ENR-50) and its cyclic dithiocarbonate derivative was carried out using NMR spectroscopy techniques. The overlapping ¹H-NMR signals of ENR-50 at δ 1.56, 1.68-1.70, 2.06, 2.15-2.17 ppm were successfully assigned. In this work, the ¹³C-NMR chemical shift assignments of ENR-50 were consistent to the previously reported work. A cyclic dithiocarbonate derivative of ENR-50 was synthesized from the reaction of purified ENR-50 with carbon disulfide (CS₂), in the presence of 4-dimethylaminopyridine (DMAP) as catalyst at reflux temperature. The cyclic dithiocarbonate formation involved the epoxide ring opening of the ENR-50. This was followed by insertion of the C-S moiety of CS₂ at the oxygen attached to the quaternary carbon and methine carbon of epoxidized isoprene unit, respectively. The bands due to the C=S and C-O were clearly observed in the FTIR spectrum while the ¹H-NMR spectrum of the derivative revealed the peak attributed to the methylene protons had split. The ¹³C-NMR spectrum of the derivative further indicates two new carbon peaks arising from the >C=S and quaternary carbon of cyclic dithiocarbonate. All other ¹H- and ¹³C-NMR chemical shifts of the derivative remain unchanged with respect to the ENR-50.     

Natural convection of nanoencapsulated phase change suspensions inside a local thermal non-equilibrium porous annulus

Journal of Thermal Analysis and Calorimetry - In this study, the heat transfer, fluid flow and heat capacity ratio are analyzed in an annulus enclosure filled with porous and saturated by a...     

Trace elements in Malaysian medicinal plants

Elemental content of twenty medicinal plants used as tonic and for treatment of diabetes and simusitis were determined by INAA and XRF. Elemental determination was carried out in the raw samples, residues after boiling and the water soluble fractions. Samples were irradiated in TRIGA MkII reactor and counted using HPGe detector coupled to Personal Computer Analyzer (PCA) system. Bowen's Kale, NBS Pine Needles, NBS Citrus Leaves SRM were analysed to check the accuracy of the techniques used. Twenty elements were determined by both NAA and XRF. Arsenic was only detected inLabisia pothoina andDracontomelon dao with a concentrations of 0.40 mg/kg and 0.60 mg/kg respectively. Antimony was found in eleven samples with a concentration of <0.20 mg/kg. Al, Br, Ca, Cl, K, Mn, Na and Rb were detected in all samples whereas Mg and Zn were present in all samples exceptCinnamomum sp. Highest concentration of Br (190 mg/kg), Cl (11805 mg/kg), Co (0.50 mg/kg), Fe (1642 mg/kg), K (36788 mg/kg), Mn (325 mg/kg), Na (126 mg/kg), Rb (197 mg/kg), Sc (0.18 mg/kg) and Zn (3551 mg/kg) were observed in the tuber ofLasia aculeata. Less than 70% and 50% of the elements contained inCallicarpa longifolia andEurycoma longifolia were obtained respectively from water by boiling.     

Studies on elemental analysis of Chinese traditional herbs by neutron activation technique and their mutagenic effect

Chinese herbs are accepted as an alternative medicine for specific treatment of illness. It is important to know the contents of these herbs that might cause gene mutation. Ten most popular herbs used in Malaysia were analyzed by instrumental neutron activation analysis. A total of 16 trace and major elements were determined and the concentration of elements varied depending on the origin of the herb. The study showed that the toxic elements found in the samples were below the levels prescribed by health regulations. The mutagenicity test showed that there was no toxic effect due to the heavy metals present in the herbs. This revised version was published online in August 2006 with corrections to the Cover Date.     

Natural radioactivity measurements in the granite rock of quarry sites,Johor, Malaysia

This study was conducted to determine the concentration of natural radionuclides in the granite rocks of selected quarry sites in Johor state, Malaysia and their possible radiological effects. The activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K in the areas of study indicated varying values of ²³⁸U, ²³²Th and ⁴⁰K. The highest values of ²³⁸U and ²³²Th concentrations (67±1 and 85±2 Bq kg^?1, respectively) were observed at Kamad Quarry (IJM), whereas the highest value of ⁴⁰K concentration (722±18 Bq kg^?1) was detected in Kim Seng Quarry, while the values of activity concentration are lower in Hanson Quarry Products (Kulai) (25±0.5 for ²³⁸U, 24±0.5 for ²³²Th and 429±11 for ⁴⁰K). Overall, ⁴⁰K has the highest concentration in the granite rocks of the quarry sites, followed by ²³²Th and the least for ²³⁸U. The radium equivalent activity concentration was found in the range between 94 and 239 Bq kg^?1, the absorbed dose rate was found to be in the range between 47 and 112 nGy h^?1, and effective dose ranged from 58 to 137 μSv h^?1. Moreover, the internal and external hazard index values were given in results lower than unity.     

Evaluation of the bioactivity of novel spiroisoxazoline typecompounds against normal and cancer cell lines

The aim of this study was to investigate the in vitro cellular activity of novel spiroisoxazoline type compounds against normal and cancer cell lines from lung tissue (Hs888Lu), neuron-phenotypic cells (SH-SY5Y), neuroblastoma (SH-SY5Y), human histiocytic lymphoma (U937), lung cancer (A549), and leukaemia (HL-60). Our bioassay program revealed that the spiroisoxazoline type compounds show cytotoxicity only in lymphoma cell lines, which is in contrast with the pyrrolidine precursor of these spiroisoxazoline compounds, where significant cytotoxicity is seen in all normal and cancer cell lines. These data suggest a tumour-specific mechanism of action. In addition these data also show that spiroisoxazoline compounds are non-toxic in the human neuronphenotypic neuroblastoma SH-SY5Y cell line, and furthermore that they might protect cells from neurodegenerative disease.     

Potential Effect of Polyphenolic-Rich Fractions of Corn Silk on Protecting Endothelial Cells against High Glucose Damage Using In Vitro and In Vivo Approaches

Endothelial cell dysfunction is considered to be one of the major causes of vascular complications in diabetes. Polyphenols are known as potent antioxidants that can contribute to the prevention of diabetes. Corn silk has been reported to contain polyphenols and has been used in folk medicine in China for the treatment of diabetes. The present study aims to investigate the potential protective role of the phenolic-rich fraction of corn silk (PRF) against injuries to vascular endothelial cells under high glucose conditions in vitro and in vivo. The protective effect of PRF from high glucose toxicity was investigated using human umbilical vein endothelial cells (HUVECs). The protective effect of PRF was subsequently evaluated by using in vivo methods in streptozotocin (STZ)-induced diabetic rats. Results showed that the PRF significantly reduced the cytotoxicity of glucose by restoring cell viability in a dose-dependent manner. PRF was also able to prevent the histological changes in the aorta of STZ-induced diabetic rats. Results suggested that PRF might have a beneficial effect on diabetic patients and may help to prevent the development and progression of diabetic complications such as diabetic nephropathy and atherosclerosis.     

Variable ranking based on the estimated degree of separation for two distributions of data by the length of the receiver operating characteristic curve

Variable responses are fundamental for all experiments, and they can consist of information-rich, redundant, and low signal intensities. A dataset can consist of a collection of variable responses over multiple classes or groups. Usually some of the variables are removed in a dataset that contain very little information. Sometimes all the variables are used in the data analysis phase. It is common practice to discriminate between two distributions of data; however, there is no formal algorithm to arrive at a degree of separation (DS) between two distributions of data. The DS is defined herein as the average of the sum of the areas from the probability density functions (PDFs) of A and B that contain a ≥ percentage of A and/or B. Thus, DS90 is the average of the sum of the PDF areas of A and B that contain ≥90% of A and/or B. To arrive at a DS value, two synthesized PDFs or very large experimental datasets are required. Experimentally it is common practice to generate relatively small datasets. Therefore, the challenge was to find a statistical parameter that can be used on small datasets to estimate and highly correlate with the DS90 parameter. Established statistical methods include the overlap area of the two data distribution profiles, Welch’s t-test, Kolmogorov–Smirnov (K–S) test, Mann–Whitney–Wilcoxon test, and the area under the receiver operating characteristics (ROC) curve (AUC). The area between the ROC curve and diagonal (ACD) and the length of the ROC curve (LROC) are introduced. The established, ACD, and LROC methods were correlated to the DS90 when applied on many pairs of synthesized PDFs. The LROC method provided the best linear correlation with, and estimation of, the DS90. The estimated DS90 from the LROC (DS90–LROC) is applied to a database, as an example, of three Italian wines consisting of thirteen variable responses for variable ranking consideration. An important highlight of the DS90–LROC method is utilizing the LROC curve methodology to test all variables one-at-a-time with all pairs of classes in a dataset.     

Rare earth element (REE) in surface mangrove sediment by instrumental neutron activation analysis

A study is carried out on the concentrations of rare earth element (REE) elements present in surface mangrove sediments from 10 locations throughout west coast Malaysia. In carrying out the analysis, the best and most convenient method being the instrumental neutron activation analysis (INAA). Samples were obtained, dried, crushed to powdery form and samples prepared for INAA. All the samples for analysis were weighted approximately 150 mg for short irradiation and 200 mg for long irradiation time. As calibration and quality control procedures, blank samples, standard reference material SL-1 were then irradiated with thermal neutron flux of 4 × 10¹² cm^?2 s^?1 at the MINT TRIGA Mark II research reactor which operated at 750 kW by using a pneumatic transport facility. The REE elements of surface sediment samples in this study are Dy, Sm, Eu,Yb, Lu, Tb, La and Ce. It was found that the level of concentrations of all the REE elements varies in the range (0.35–117.4 mg/kg). The geochemical behavior of REEs in surface sediments and normalized pattern (chondrite and shale) has been studied. The degree of sediments contaminations were computed using an enrichment factor. The results showed that the enrichment factor varied in the range (0.75–6.75).