In order to complete having data base of elemental assessment of the east coast of Peninsular Malaysia marine sediments along
the South China Sea coasts, trace elements are analyzed and their distribution in marine sediments is undertaken. The present
study is done parallel with pervious study on elemental assessment of heavy metals, rare earth elements and actinides in the
marine sediments of the east coast of Peninsular Malaysia. Thirty surface sediment samples were collected in this area, including
regions of Kelantan, Terengganu, Pahang, Rompin and Johor Baharu. Multielemental analysis was carried out by instrumental
neutron activation analysis and inductively coupled plasma atomic emission spectroscopy. In both cases methodology validation
was performed by certified reference material analyses. For the surface elemental distributions the enrichment factor values,
average Igeo and mCd values indicate that the trace elements of the surface sediments are uncontaminated in all sampling stations that are consistent
with previous studies results of heavy metals, rare earth elements and actinides. 相似文献
This paper proposes the chaos control and the modified projective synchronization methods for unknown heavy symmetric chaotic
gyroscope systems via Gaussian radial basis adaptive backstepping control. Because of the nonlinear terms of the gyroscope
system, the system exhibits chaotic motions. Occasionally, the extreme sensitivity to initial states in a system operating
in chaotic mode can be very destructive to the system because of unpredictable behavior. In order to improve the performance
of a dynamic system or avoid the chaotic phenomena, it is necessary to control a chaotic system with a regular or periodic
motion beneficial for working with a particular condition. As chaotic signals are usually broadband and noise-like, synchronized
chaotic systems can be used as cipher generators for secure communication. Obviously, the importance of obtaining these objectives
is specified when the dynamics of gyroscope system are unknown. In this paper, using the neural backstepping control technique,
control laws are established which guarantees the chaos control and the modified projective synchronization of unknown chaotic
gyroscope system. In the neural backstepping control, Gaussian radial basis functions are utilized to on-line estimate the
system dynamic functions. Also, the adaptation laws of the on-line estimators are derived in the sense of Lyapunov function.
Thus, the unknown chaotic gyroscope system can be guaranteed to be asymptotically stable. Also, the control objectives have
been achieved. 相似文献
A method based on direct immersion solid‐phase microextraction (DI‐SPME) coupled with high performance liquid chromatography combined with post‐column photochemically induced fluorimetry derivatization and fluorescence detection (HPLC‐PIF‐FD) was developed to extract three pyrethroid insecticides, i.e. cyfluthrin, cypermethrin, and flumethrin from water samples. A sol‐gel based coating fiber using 3‐(trimethoxysilyl propyl) amine as precursor was prepared and used for the extraction of the pyrethroids from groundwater samples. A post‐column photochemical reactor was designed and constructed for the derivatization of these environmentally important pollutants to increase their fluorescence sensitivity and determination in HPLC. The parameters affecting extraction process (extraction time and temperature, pH, salt addition, and co‐solvent) and desorption step (solvent, desorption time, and temperature) of the analytes from the sol‐gel‐based fiber, along with photochemical reaction conditions were investigated. The developed method proved to be relatively rapid, simple, and easy and offers high sensitivity and reproducibility. Linear dynamic ranges (LDR) for these insecticides were ranged between 0.25 to 50 μg/L. The regression coefficients were satisfactory (R2 > 0.984) for these pyrethroids. The limits of detection and limits of quantification varied between 0.09 and 0.35 μg/L and 0.25 and 1.00 μg/L, respectively. Relative standard deviation RSDs values varied between 4.41% and 6.20%. Relative recoveries obtained from analysis of Jajroud river water sample ranged between 94% and 104%. 相似文献
In order to evaluate the influence of static magnetic fields (SMF) on the progression of cell cycle as a monitor of presumptive genotoxicity of these fields, the effects of a 15 mT SMF on cell cycle progression in rat bone marrow stem cells (BMSC) were examined. The cells were divided into two groups. One group encountered SMF alone for 5 h continuously but the other group exposed with X ray before treatment with SMF. The population of cells did not show any significant difference in the first group but the second group that was exposed with acute radiation before encountering SMF showed a significant increase in the number of cells in G2/M phase. So SMF has intensified the effects of X ray, where SMF alone, did not had any detectable influence on cell cycle.These findings suggest that magnetic fields (MF) play their role by increasing the effects of genotoxic agents and because of the greater concentration of free radicals in the presence of radical pair producers, this effect is better detectable. 相似文献
The major drawback of the s-step iterative methods for nonsymmetric linear systems of equations is that, in the floating-point arithmetic, a quick loss
of orthogonality of s-dimensional direction subspaces can occur, and consequently slow convergence and instability in the algorithm may be observed
as s gets larger than 5. In [18], Swanson and Chronopoulos have demonstrated that the value of s in the s-step Orthomin(k) algorithm can be increased beyond s=5 by orthogonalizing the s direction vectors in each iteration, and have shown that the ATA-orthogonal s-step Orthomin(k) is stable for large values of s (up to s=16). The subject of this paper is to show how by using the CADNA library, it is possible to determine a good value of s for
ATA-orthogonal s-step Orthomin(k), and during the run of its code to detect the numerical instabilities and to stop the process correctly,
and to restart the ATA-orthogonal s-step Orthomin(k) in order to improve the computed solution. Numerical examples are used to show the good numerical properties.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
A headspace solid-phase dynamic extraction (HS-SPDE) technique was developed by the use of polypyrrole (PPy) sorbent, electropolymerized inside the surface of a needle, as a possible alternative to solid-phase microextraction (SPME). Thermal desorption was subsequently, employed to transfer the extracted analytes into the injection port of a gas chromatography-mass spectrometry (GC-MS). The PPy sorbent including polypyrrole-dodecyl sulfate (PPy-DS) was deposited on the interior surface of a stainless steel needle from the corresponding aqueous electrolyte by applying a constant deposition potential. The homogeneity and the porous surface structure of the coating were examined using the scanning electron microscopy (SEM).The developed method was applied to the trace level extraction of some polycyclic aromatic hydrocarbons (PAHs) from aqueous sample. In order to enhance the extraction efficiency and increase the partition coefficient of analytes, the stainless steel needle was cooled at 5 °C, while the sample solution was kept at 80 °C. Optimization of influential experimental conditions including the voltage of power supply, the time of PPy electrodeposition, the extraction temperature, the ionic strength and the extraction time were also investigated. The detection limits of the method under optimized conditions were in the range of 0.002-0.01 ng mL−1. The relative standard deviations (R.S.D.) at a concentration level of 0.1 ng mL−1 were obtained between 7.54 and 11.4% (n = 6). The calibration curves of PAHs showed linearity in the range of 0.01-10 ng mL−1. The proposed method was successfully applied to the extraction of some selected PAHs from real-life water samples and the relative recoveries were higher than 90% for all the analytes. 相似文献
Journal of Solid State Electrochemistry - In this work, the asymmetric supercapacitor (ASC) devices with three different electrolytes including aqueous, organic, and gel polymer electrolytes have... 相似文献
The solubility of sildenafil citrate (SC) in aqueous mixtures of propylene glycol (PG) was investigated. This study was carried out at different mass fractions of PG ranging from 0.1 to 0.9 at T = 293.2–313.2 K. The solubility of SC in the mixed solutions increased with increasing temperature and PG mass fraction.
The solubility values were correlated by two co-solvency models (Jouyban–Acree model and van’t Hoff–Jouyban–Acree model). The mean relative deviations (MRD) were 5.7% and 5.5%, respectively. Density of the SC-saturated solutions over the entire solvent composition and temperature range was also measured and the results correlated with the Jouyban–Acree model. Furthermore, the apparent thermodynamic properties, dissolution enthalpy, dissolution entropy and Gibbs free energy change of dissolution process of SC in all the mixed solvents were calculated according to van’t Hoff and Gibbs equations. Dissolution of SC in these mixed solvents is an endothermic process. 相似文献
A novel amino-functionalized polymer was synthesized using 3-(trimethoxysilyl) propyl amine (TMSPA) as precursor and hydroxy-terminated polydimethylsiloxane (OH-PDMS) by sol–gel technology and coated on fused-silica fiber. The synthesis was designed in a way to impart polar moiety into the coating network. The scanning electron microscopy (SEM) images of this new coating showed the homogeneity and the porous surface structure of the film. The efficiency of new coating was investigated for headspace solid-phase microextraction (SPME) of some environmentally important chlorophenols from aqueous samples followed by gas chromatography–mass spectrometry (GC–MS) analysis. Effect of different parameters influencing the extraction efficiency such as extraction temperature, extraction time, ionic strength and pH was investigated and optimized. In order to improve the separation efficiency of phenolic compounds on chromatography column all the analytes were derivatized prior to extraction using acetic anhydride at alkaline condition. The detection limits of the method under optimized conditions were in the range of 0.02–0.05 ng mL−1. The relative standard deviations (R.S.D.) (n = 6) at a concentration level of 0.5 ng mL−1 were obtained between 6.8 and 10%. The calibration curves of chlorophenols showed linearity in the range of 0.5–200 ng mL−1. The proposed method was successfully applied to the extraction from spiked tap water samples and relative recoveries were higher than 90% for all the analytes. 相似文献