A study on effect of sonochemistry in a reverberation field

In this paper,an ultrasound with frequency of 815 kHz was used to re-search the sonochemical yield in a small-size reverberation field by the methodof fluorescent spectrum analysis.There are two characteristics on the effect ofsonochemistry in the reverberation field:First,the cavitation threshold wasabout 0.3W/cm~2(it was 0.7W/cm~2 in travelling field);Second,when thesound intensity was larger than the threshold,the sonochemical yield increasedas the intensity increased and increased rapidly after the intensity was at1.69-2.13W/cm~2,so that there was a upturned point in the curve of the result(which would tend to saturation in the travelling field).The theoretical analysisshows that the reason of the threshold decrease is that the sound energy densitybecomes high in the reverberation field,and the upturned point results from thedisturbance of the radiation pressure on the liquid surface.Therefore,by exper-iment and theory this paper shows that a reverberation field has to be built forthe higher sonoche     

X射线和过氧化氢引起的Hela细胞染色质损伤的微区拉曼光谱研究

我们成功地用微区拉曼光谱探针技术获得了培养单个活体 Hela 细胞核中染色质的拉曼光谱。从光谱中我们看到正常 Hele 细胞核蛋白的二级结构为 a 螺旋,DNA 为 A 型构象。经10~(-3)moI/L 过氧化氢处理20分钟及8Gy x 射线照射后的 Hela 细胞核蛋白的二级结构出现反平行β折叠,DNA 出现 B 型构象。这种结果与我们的假设是相符合的。     

A quantitative study on the effect of nitrogen concentration on two-dimensional electron gas (2DEG) mobility in a dilute nitride GaAsN/AlGaAs heterostructure

Detailed theoretical analysis of the temperature dependence of two-dimensional electron gas mobility data in GaAs_1−xN_x/Al_0.38Ga_0.62As samples (x=0, 0.1% and 0.4%) shows that, as x increases, the dislocation density and the number of ionized impurities in the potential well increase by a factor of ∼ ×300 and ∼ ×500, respectively.     

A study on quantitative analysis of exposure dose caused by patient depending on time and distance in nuclear medicine examination

This study evaluated possible actions that can help protect against and reduce radiation exposure by measuring the exposure dose for each type of isotope that is used frequently in nuclear medicine before performing numerical analysis of the effective half-life based on the measurement results. From July to August in 2010, the study targeted 10, 6 and 5 people who underwent an ¹⁸F-FDG (fludeoxyglucose) positron emission tomography (PET) scan, ^99mTc-HDP bone scan, and ²⁰¹Tl myocardial single-photon emission computed tomography (SPECT) scan, respectively, in the nuclear medicine department. After injecting the required medicine into the subjects, a survey meter was used to measure the dose depending on the distance from the heart and time elapsed. For the ¹⁸F-FDG PET scan, the dose decreased by approximately 66% at 90 min compared to that immediately after the injection and by 78% at a distance of 1 m compared to that at 0.3 m. In the ^99mTc-HDP bone scan, the dose decreased by approximately 71% in 200 min compared to that immediately after the injection and by approximately 78% at a distance of 1 m compared to that at 0.3 m. In the ²⁰¹Tl myocardial SPECT scan, the dose decreased by approximately 30% in 250 min compared to that immediately after the injection and by approximately 55% at a distance of 1 m compared to that at 0.3 m. In conclusion, the dose decreases by a large margin depending on the distance and time. In conclusion, this study measured the exposure doses by isotopes, distance from the heart and exposure time, and found that the doses were reduced significantly according the distance and the time.     

A study on quantitative analysis of field size and dose by using gating system in 4D conformal radiation treatment

This study evaluated the gating-based 4-D conformal radiation therapy (4D-CT) treatment planning by a comparison with the common 3-D conformal radiation therapy (3D-CT) treatment planning and examined the change in treatment field size and dose to the tumors and adjacent normal tissues because an unnecessary dose is also included in the 3-D treatment planning for the radiation treatment of tumors in the chest and abdomen. The 3D-CT and gating-based 4D-CT images were obtained from patients who had undergone radiation treatment for chest and abdomen tumors in the oncology department. After establishing a treatment plan, the CT treatment and planning system were used to measure the change in field size for analysis. A dose volume histogram (DVH) was used to calculate the appropriate dose to planning target volume (PTV) tumors and adjacent normal tissue. The difference in the treatment volume of the chest was 0.6 and 0.83 cm on the X- and Y-axis, respectively, for the gross tumor volume (GTV). Accordingly, the values in the 4D-CT treatment planning were smaller and the dose was more concentrated by 2.7% and 0.9% on the GTV and clinical target volume (CTV), respectively. The normal tissues in the surrounding normal tissues were reduced by 3.0%, 7.2%, 0.4%, 1.7%, 2.6% and 0.2% in the bronchus, chest wall, esophagus, heart, lung and spinal cord, respectively. The difference in the treatment volume of the abdomen was 0.72 cm on the X-axis and 0.51 cm on the Y-axis for the GTV; and 1.06 cm on the X-axis and 1.85 cm on the Y-axis for the PTV. Therefore, the values in the 4D-CT treatment planning were smaller. The dose was concentrated by 6.8% and 4.3% on the GTV and PTV, respectively, whereas the adjacent normal tissues in the cord, Lt. kidney, Rt. kidney, small bowels and whole liver were reduced by 3.2%, 4.2%, 1.5%, 6.2% and 12.7%, respectively. The treatment field size was smaller in volume in the case of the 4D-CT treatment planning. In the DVH, the 4D-CT treatment planning showed a higher dose concentration on the part to be treated than the 3D-CT treatment planning with a lower dose to the adjacent normal tissues. Overall, the gating-based 4D-CT treatment planning is believed to be more helpful than the 3D-CT treatment planning.     

A high-resolution X-ray scattering study of the effect of defects on the first-order transition in KMnF3

A high-resolution X-ray scattering study of the influence of impurities on the cubic to tetragonal first-order phase transition of KMnF₃ is presented. It is shown that Ca⁺⁺ ions substituted for Mn⁺⁺ or Na⁺ ions substituted for K⁺ ions at a 1% concentration can influence drastically both the nature and the critical fluctuations of this transition. A qualitative attempt of interpretation in terms of random stress effects is presented.     

A study on the effect of stress state on damage evolution in hot deformation of free cutting steels using double notched bars

The effect of stress state on the initiation of damage for leaded free cutting steel has been investigated under hot rolling conditions. Double notched (DN) circumferential tension samples were designed and used to simulate damage development at different stress states and deformation conditions using a Gleeble (3800) thermal-mechanical testing system. Two DN sample geometries with varying notch profiles were used to account for different states of stress. To simulate the conditions of hot rolling the samples were tested at high temperatures (900–1200 °C) and moderate strain rates (0.1–1 s^?1). After testing to failure, which normally occurs at one notch of the specimen, the unfailed notch of each sample was sectioned to examine the sites where damage occurs since the material has been captured in a state very close to failure. Two of the cases examined have shown definitive damage paths occurring from ‘outside–in’ for a sharp notch deformed at T = 900 °C and from ‘inside–out’ for a blunt notch tested at T = 1200 °C for the same strain rate of 0.1 s^?1. The experimental results of the failure initiation sites were compared with computed values of the stress fields around the notch profiles, obtained from FE analysis using a set of viscoplastic constitutive equations calibrated for free cutting steel. The temperature profiles from high temperature mechanical testing were used in the FE calculations of the stress state.     

A study of the effect of axial mode spacing on the single longitudinal mode performance in end pumped solid-state lasers

In this paper, we present the study of the effect of axial mode spacing on the performance of a single longitudinal mode (SLM) laser in an end pumped solid-state laser system. We present a theoretical analysis of an SLM laser for arbitrary values of axial mode spacing, which predicts that the ratio of the maximum pump power up to which SLM operation is possible to the pump power at the lasing threshold is strongly dependent on the axial mode separation. We also present the results of a study where a temperature controlled birefringent filter was used to increase the axial mode spacing in a diode end pumped solid-state laser system, resulting in an enhancement of the SLM laser performance.     

Excited-state hydrogen bonding effect on dynamic fluorescence of coumarin 102 chromophore in solution: A time-resolved fluorescence and theoretical study

The steady-state absorption and emission as well as the time-resolved fluorescence spectra of coumarin 102 (C102) in both aprotic and alcoholic solvents have been used to study the effect of excited-state hydrogen bond on the dynamic fluorescence of C102 chromophore in various solutions. The dual fluorescence of C102 in alcohols, which is dependent on the hydrogen-bonded donation ability of the solvent, has been assigned to the distribution of free C102 and a hydrogen-bonded complex. Furthermore, a shift of the fluorescence spectra induced by excited-state hydrogen bond has been demonstrated to take place within hundreds of picoseconds by the performance of the time-resolved fluorescence spectra with the time-correlated single-photon-counting (TCSPC) technique. Moreover, the time-dependent density functional theory (TDDFT) has been used to calculate the hydrogen-bonded equilibrium constant pK_HB in different electronic states. It has been demonstrated for the first time that the hydrogen bond strengthening in electronic excited states could decrease the free energy of the hydrogen-bonded complex due to its stronger binding energy. Therefore, the hydrogen-bonded equilibrium will become markedly in favor of the hydrogen-bonded forms in electronic excited states by comparison with the case in the ground state.     

A numerical study on the effect of CO addition on extinction limits and NO x formation in lean counterflow CH4/air premixed flames

The effect of CO addition on extinction and NO _x formation in lean premixed counterflow CH₄/air flames was investigated by numerical simulation. Detailed chemistry and complex thermal and transport properties were employed. A method that gradually switched off the initial reactions of NO formation from different routes was used to analyse the variation of NO formation mechanism. The results indicate that the addition of certain amount of CO increases the strain extinction limits and reduces the radiation extinction limits. As a result, the lean flammability limit of CH₄/air premixed flame is extended to leaner side by the addition of CO. The formation of NO in a flame is increased with the addition of CO at a constant equivalence ratio. For an ultra-lean flame, the increase in the formation of NO is mainly because of the increase in the contribution from the NNH intermediate route, while for a near stoichiometric flame, this increase is mainly attributable to the rise in the contribution from the thermal route. With the fraction of added CO being gradually increased, the formation of NO₂ in a flame first decreases and then increases at a given equivalence ratio. The addition of CO reduces the formation N₂O in an ultra-lean flame, while affects little on the formation of N₂O in a near stoichiometric flame.     

A study on the blending effect of polyvinyledene fluoride in the ionic transport mechanism of plasticized polyvinyl chloride + lithium perchlorate gel polymer electrolytes

The gel polymer electrolytes composed of the blend of polyvinylchloride (PVC) and polyvinylidene fluoride (PVdF) as host polymers, the mixture of ethylene carbonate (EC) and propylene carbonate (PC) as a plasticizer, and LiClO₄ as a salt was studied. An attempt was made to investigate the effect of PVdF in the plasticized PVC + LiClO₄ system in three blend ratios. The differential scanning calorimetry study confirms the formation of polymer–salt complex and miscibility of the PVC and PVdF. The X-ray diffraction results of plasticized PVC (S1, S2, S3) and PVdF-blended films (S4, S5, S6) were compared, in that an increase in PVC concentration decreases the degree of crystallinity for S1 and S3, respectively, but drastically increases for PVC (S2). The increase in PVC content has not accounted in the conductivity studies also noted. However, the blending effect of PVdF showed decreases in crystallinity homogeneously for (S6 > S5 > S4), which were reflected in ionic conductivity measurements. The surface morphology of the films were also studied by scanning electron microscope, and it corroborates the same. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

The effect of NO/O2 ratio in NO-CO-O2 reaction on a catalytic surface: A computer simulation study

The interaction among the reacting species in the NO-CO-O₂ reaction on a metal catalytic surface that proceeds according to the Langmuir-Hinshelwood mechanism is studied by means of Monte Carlo simulation. The study of this three-component system is essential for the understanding of the influence of NO/O₂ ratio on the catalytic reduction of NO into N & O and oxidation of CO to CO₂. It is found that this complex system, which has not been studied on these lines before, exhibits irreversible phase transitions between active states with sustained reaction and poisoned states with the catalytic surface fully covered by the reactants. The phase diagrams of the surface coverage with CO, N or O and the steady state production of CO₂ are evaluated as a function of the partial pressure of CO in the gas phase. From this study, it is observed that with the addition of NO in the CO-O₂ reaction, the critical points in the phase diagram move towards lower values of CO partial pressure but the width of reaction window remains almost the same. However, the maximum production rate of CO₂ decreases continuously. On the other hand, the addition of O₂ in the NO-CO reaction shifts the critical points towards higher values of CO pressure. Moreover, the width of reaction window as well as the production rate of CO₂ increases with the increase in O₂ concentration.     

A study of the stability of pyrolytic carbon-coated Fe/SiO2 composites in HNO3 and the effect of pyrolysis temperatures on their magnetic properties

Fe/SiO₂ composites prepared by a sol-gel combined hydrogen reduction method were coated with carbon by the pyrolysis of acetylene. Scanning electron microscopy (SEM) showed that the as-prepared sample consists of only carbon-coated Fe/SiO₂ particles without the presence of one-dimensional carbon or any other unwanted carbon formation. The stability of the Fe/SiO₂ composites under a HNO₃ solution at room temperature was greatly enhanced after they were coated with carbon. The effect of pyrolysis temperatures was also studied.     

A comprehensive study of the effect of <Emphasis Type="Italic">in situ</Emphasis> annealing at high growth temperature on the morphological and optical properties of self-assembled InAs/GaAs QDs

We investigate the effect of in situ annealing during growth pause on the morphological and optical properties of self-assembled InAs/GaAs quantum dots (QDs). The islands were grown at different growth rates and having different monolayer coverage. The results were explained on the basis of atomic force microscopy (AFM) and photo-luminescence (PL) measurements. The studies show the occurrence of ripening-like phenomenon, observed in strained semiconductor system. Agglomeration of the self-assembled QDs takes place during dot pause leading to an equilibrium size distribution. The PL properties of the QDs are affected by the Indium desorption from the surface of the QDs during dot pause annealing at high growth temperature (520°C) subsiding the effect of the narrowing of the dot size distribution with growth pause. The samples having high monolayer coverage (3.4 ML) and grown at a slower growth rate (0.032 ML s⁻¹) manifested two different QD families. Among the islands the smaller are coherent defect-free in nature, whereas the larger dots are plastically relaxed and hence optically inactive. Indium desorption from the island surface during the in situ annealing and inhomogeneous morphology as the dots agglomerate during the growth pause, also affects the PL emission from these dot assemblies.