以脉冲萃取柱利用三异辛胺从高浓度铀溶液中回收铀

利用三异辛胺(TOA)纯化Gattar小型试验工厂的高浓度铀溶液(洗脱液的铀浓度7 g·L^-1),研究了脉冲萃取柱的性能。利用实验室级脉冲萃取柱进行了实验室规模的溶剂萃取实验和后续实验。结果表明,在室温、pH=1和有机相与水相的比例(V_O/V_A)约为1.8：1时,加入二(2-乙基己基)磷酸(D2EHPA)使其与TOA的比例(V_D2EHPA/V_TOA)为2：3,可使萃取克服Cl-的抑制效应,提高效率。将结论用于考察试验工厂级萃取柱的流体力学和传质性能,结果表明用脉冲萃取柱萃取铀可以达到97%的萃取效率,具有可行性。     

DFT investigation of NH3 physisorption on CuSO4 impregnated SiO2

In this quantum chemical investigation, NH(3) physisorption onto a model of copper sulfate impregnated silica is compared with pure silica and copper sulfate adsorbents. The physisorption process is modeled as direct binding of the NH(3) molecule to the adsorption site of the dry adsorbents and as displacement of a H(2)O molecule by NH(3) in the hydrated complexes. The surface of silica is represented by a hydroxyl group attached to a silsesquioxane cage, H(7)Si(8)O(12)(OH) and silica impregnated with CuSO(4) by the most stable configuration of the cluster containing a CuSO(4) ion pair placed adjacent to the silica cage. H(2)O is systematically added to the dehydrated adsorbents to investigate the role of water in NH(3) adsorption. Modeling hydrated environments of each type of adsorbent is focused on H(2)O molecules that directly coordinate with the active sites. The results indicate that the binding energy of adsorbing NH(3) onto the mixed adsorbent is greater than in pure silica. This enhanced binding in the mixed adsorbent is consistent with improved Br?nsted acidity of the silanol in the presence of CuSO(4).     

Characterization of small-signal intensity modulation of single-mode fiber grating Fabry-Perot laser source

A comprehensive study on the small-signal intensity modulation (IM) characteristics of a fiber grating Fabry-Perot (FGFP) laser is numerically investigated. The effect of external optical feedback (OFB), temperature, injection current, cavity volume, nonlinear gain compression factor, and fiber grating (FG) parameters on IM characteristics are presented. The temperature dependence (TD) of IM is calculated according to the TD of laser cavity parameters instead of using the well-known Parkove relationship. It has been shown that the optimum external fiber length (L _ext) is 3.1 cm. The optimum range of working temperature for FGFP laser is between 23 to 27 °C. We also show that by increasing the laser injection current from 10 to 60 mA, the IM peak amplitude decreased from 6.3 to 0.2 dB and the relaxation-oscillation frequency (ROF) is shifted from 1.2 GHz towards higher frequency of 5.48 GHz. In addition, the AR coating reflectivity and gain compression factor have no significant effect on the IM. The study indicates that a stable operation and excellent modulation characteristic can be obtained after optimization process.     

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.     

Labeling of new formulation of tin–sucralfate freeze-dried kit with technetium-99m and its biological evaluation

The present investigation deals with a simple preparation of new formulation of tin?Csucralfate freeze-dried kit (F.D.K.), to be directly labeled with ^99mTc at optimal pH value of 7.0. The lyophilized form containing 100?mg sucralfate and 11.3?mg dihydrated stannous chloride. Other optimal pH values of the preparation were found to be from 4.0 to 11.0. The range of sucralfate amount studied (50?C500?mg) not affected the radiochemical purity of the labeled complex. The radiochemical purity and the stability of the labeled preparation that assessed by filtration were more than 95%. ^99mTc sucralfate was radiochemical stable up to a specific activity of 1,000?mCi per gram which was more stable than earlier published value (700?mCi per gram) without any radiolytic decomposition. The biological behavior of ^99mTc-pertechnetate was evaluated in two groups of animals, the first group (neither fasted nor ulcerated) and the second group (fasted and ulcerated mice). The data of organ distribution of ^99mTc?Csucralfate in ulcerated fasted mice showed that more than 99% of the administered dose was accumulated in the stomach (87.92%) and intestine (11.43%). The radioanalytical results together with the in vivo-biological behavior of the labeled preparation demonstrate it??s stability, efficacy and usefulness in medical applications for the detection of gastrointestinal ulcers.     

1,1‐Di(9‐fluorenyl)­ethanol,a ­by‐­product from the acetyl­ation of 9‐fluorenyl­lithium

Treatment of 9‐fluorenyl­lithium with acetyl chloride produces 9‐acetyl­fluorene, (I), and several by‐products. Among them is a compound unequivocally identified for the first time as the addition product of (I) with 9‐fluorenyl­lithium, 1,1‐di(9‐fluorenyl)­ethanol, C₂₈H₂₂O, (II). The two fluorene‐ring planes of (II) are essentially perpendicular [89.90 (9)°]. A number of intermolecular non‐bonding distances are well within or close to the sum of their respective van der Waals radii and may be responsible for the rarely observed large bowing of one of the fluorene rings. This bowing apparently arises from two mol­ecules impinging on the convex face of the bowed ring, augmented by hydrogen bonding between the peripheral π electrons of the concave face and the hydroxyl H atom of another mol­ecule adjacent to that face.     

Highly sensitive label-free in vitro detection of aflatoxin B1 in an aptamer assay using optical planar waveguide operating as a polarization interferometer

Analytical and Bioanalytical Chemistry - This work reports on further development of an optical biosensor for the in vitro detection of mycotoxins (in particular, aflatoxin B1) using a highly...     

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.