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1.
In this investigation, the concentration levels of potassium, calcium, iron, nickel and cadmium for three Chrysolina species were measured in the region of Erzurum (Turkey) located at latitude 40°17′ north and longitude 41°17′ east. The concentrations measured by energy dispersive X-ray fluorescence (EDXRF) spectrometry were analysed. Photons of 59.5 keV and 5.9 keV emitted, respectively, by an annular 241Am and 55Fe radioactive source were used to excite the characteristic X-rays of various elements present in the insect samples. These results are presented and discussed in this paper.  相似文献   

2.
The Coster-Kronig (CK) enhancement effect was measured for L3 subshell X-rays using the experimental Lα X-ray production cross-section, the fraction of Lα X-rays, L3 subshell fluorescence yields and L3 subshell photoionisation cross-section. The samples were excited by gamma-rays with 59.5 keV energy from a 75 mCi radioisotope source and L X-rays emitted from samples were counted by a Si(Li) detector with resolution 155 eV at 5.96 keV. Variation of enhancement effect of CK transition of L3 X-rays of La and Ce compounds was measured to be more than that of Ba. Ba has a partially filled 6s orbital whereas La and Ce have partially filled 5d and 4f orbitals, respectively.  相似文献   

3.
Using the ab initio FLAPW-GGA method we examine the electronic band structure, densities of states, and the Fermi surface topology for a very recently synthesized ThCr2Si2-type potassium intercalated iron selenide superconductor KxFe2Se2. We found that the electronic state of the stoichiometric KFe2Se2 is far from that of the isostructural iron pnictide superconductors. Thus the main factor responsible for experimentally observed superconductivity for this material is the deficiency of potassium, i.e. the hole doping effect. On the other hand, based on the results obtained, we conclude that the tuning of the electronic system of the new KxFe2Se2 superconductor in the presence of K vacancies is achieved by joint effect owing to structural relaxations and hole doping, where the structural factor is responsible for the modification of the band topology, whereas the doping level determines their filling.  相似文献   

4.
In this paper, the interaction between different organic and inorganic K/S/Cl compounds in the solid structure of biomass is studied and a model is presented to predict the temporal release of Kg, HCl, CH3Cl, KCl, KOH, K2SO4 and SO2 from biomass devolatilization. Four types of pulverized biomass are chosen from literature, two of which have no chlorine content and two with chlorine content in lower stoichiometry to potassium. The results of the model are compared with the experimental measurements. In the presence of chlorine, KCl, HCl and Kg were found to be the dominant chlorine and potassium species. In the absence of chlorine, Kg dominates the release of potassium. KOH and K2SO4 release into the gas phase towards the end of devolatilization due to the overlapping with char combustion. SO2 is the main sulfur species released into the gas phase. The model is coupled with a CFD solver where the gas phase chemistry of the K/S/Cl system can be studied using available chemical mechanisms for these species.  相似文献   

5.
The removal efficiency of Viscumalbum L. from lead containing aqueous solutions was investigated. The effect of adsorbent mass, pH of solution, initial Pb(II) concentration and temperature was investigated using a batch adsorption technique. The optimum pH for Pb(II) adsorption was found as 3.0 for Viscumalbum L. Results were analyzed by the Langmuir, Freundlich, Temkin and Harkins-Jura, equation using linearized correlation coefficient at different temperature. The characteristic parameters for each isotherm have been determined. The Langmuir model agrees very well with experimental data than the other models. According to Langmuir isoterm, the monolayer saturation capacity (Qo) is 769.23 mg/g at 25 °C. Models and the isotherm constant were evaluated depending on temperature. Thermodynamic parameters such as ΔHo, ΔSo and ΔGo were calculated. The adsorption process was found to be endothermic and spontaneous. The experimental data were analyzed using the first- and the second-order kinetic models. The rate constants of adsorption for both kinetics models have been calculated. The second-order model provides the best correlation of the data.  相似文献   

6.
and X-rays of calcium were produced by bombarding a thick calcium wafer with oxygen, helium and hydrogen ions. These reactions produce a substantial amount of inner shell ionization. TheK X-ray spectra contain X-ray lines from calcium which emanate from initial states with a varying degree ofK orL shell vacancies. The initial configurations were assigned on the basis of Hartree-Fock-Slater calculated energies. Related intensity ratio of1s→2p (Kα) transitions and of1s→3p () transitions of H plus Ca, He plus Ca and O plus Ca were obtained. In addition to observing many new transitions due to multipleK and/or multipleL shell vacancies, energy shifts relative to the H plus Ca spectrum were observed in the O plus Ca spectrum due toM shell vacancies.  相似文献   

7.
In order to investigate whether tea (Camellia sinensis (L.) Kuntze) dust particles could be a possible carrier of the pathogen contaminated Mycobacterium a biotechnical procedure was used, and to verify the possibility of monitoring this dust, a laser based light scattering setup was designed and fabricated. Experiments were carried out using the strain Mycobacterium smegmatis mc2 155 as a model organism to study the effect on tea dust particles. Light scattering investigations on both M. smegmatis contaminated and uncontaminated tea dust particle samples were carried out as a function of scattering angle at 543.5, 594.5 and 632.5 nm wavelengths. The results have shown that the behavior of tea dust samples both with and without Mycobacterium varies significantly for all the three different incident laser wavelengths.  相似文献   

8.
We have performed a comparative investigation of the series compounds (InSb)nCum to assess the roles of Cu addition on the thermoelectric properties and nanostructuring in bulk InSb. Detailed temperature dependent transport properties including electrical conductivity, the Seebeck coefficient, and thermal conductivity are presented. The Seebeck coefficients of In20Sb20Cu (m:n = 1:20) are increased by 13 percent in magnitude if compared to those of InSb, which is responsible for the 22 percent enhancement in the highest ZT value at 687 K. Although the magnitudes of κL are larger than those of InSb over the entire temperature range, a remarkable reduction in lattice thermal conductivities (κL) was observed with measuring temperature elevation. Such changes are mainly due to the precipitation of a large number of Cu9In4 nanoparticles with the size of smaller than 5 nm, dispersed in the matrix observed using high resolution transmission electron microscopy (HRTEM) images.  相似文献   

9.
The samples of Cu1−xPtxFeO2 (0 ≤ x ≤ 0.05) delafossite have been synthesized by solid-state reaction method to investigate their optical and electrical properties. The properties of electrical resistivity and Seebeck coefficient were measured in the high temperature ranging from 300 to 960 K, and the Hall effect and the optical properties were measured at room temperature. The obtained results of Seebeck showed the samples are p-type conductor. The optical properties at room temperature exhibited the samples are transparent visible light material with optical direct gap 3.45 eV. The low electrical resistivity, hole mobility and carrier density at room temperature displayed value ranging from 0.29 to 0.08 Ω cm, 1.8 to 8.6 cm2/V s and 1.56 × 1018 to 4.04 × 1019 cm−3, respectively. The temperature range for transparent visible light is below 820 K because the direct energy gap contains value above 3.1 eV. Consequently, the Cu1−xPtxFeO2 delafossite enhance performance for materials of p-type transparent conducting oxide (TCO) with low electrical resistivity.  相似文献   

10.
The detection of xenon K and L X-rays from a magnetically confined ring of relativistiv electrons loaded with Xe ions is reported. From the ratio of intensities of L and K X-rays, the ratio of cross-sections for L and K vacancy production in Xe by 7.5 MeV electrons was determined to be σL/σK = 18 ± 8.  相似文献   

11.
New blue-green emitting Sr4Al14O25:Ce3+ phosphor is reported in this paper. The polycrystalline samples of phosphor were prepared by the conventional solution combustion method and checked for crystallization and phase by X-ray diffraction. Photoluminescence studies reveal the emission at 472 and 511 nm that correspond to the transition between lowest T2g level of the 5d state to the 2F5/2 and 2F7/2 ground state levels of the Ce3+. The excitation at 275 nm corresponds to O2−→Ce4+ charge transfer processes to lowest 5d state of Ce ion (T2g). Phosphorescence decay procedures reveal the existence of slow, medium, and fast component involved in the process. Varying the γ-dose (1-6 Gy), thermoluminescence (TL) measurements were made and glow curve maximum is obtained at 383 K. The phosphor seems to follow a first-order kinetics due to non-shifting Tm property. The Tm-Tstop method followed by the repeated initial rise method is applied to determine the distribution of activation energies and corresponding maximum positions. Chi-square minimization procedures provide the appropriate peak positions and other trapping parameters. From deconvolution results, the activation energies are found to be 0.84 and 1.06 eV, while the frequency factor is of the order of 1010 and 1011 s−1, respectively.  相似文献   

12.
The thermal expansion and magnetostriction of HoFe11−xCoxTi (x=0, 0.3, 0.7 and 1) intermetallic compounds were measured, using the strain gauge method in the temperature range 77–590 K under applied magnetic fields up to 1.5 T. Results show that for samples with x=0 and 0.3, both linear thermal expansion and linear thermal expansion coefficient exhibit anomalies below the Curie temperature. Below room temperature, the spontaneous volume magnetostriction decreases with Co content. For all compounds studied, the anisotropic magnetostriction shows similar behaviour in the measured temperature range. The magnetostriction compensation occurs above room temperature in all samples. The volume magnetostriction shows a linear dependence on the applied field and by approaching the Curie temperature this trend changes to parastrictive behaviour. The results of the spontaneous magnetostriction are discussed based on the local magnetic moment model. The contribution of magnetostriction attributed to the magnetic sublattices R and T (Fe or Co) is discussed.  相似文献   

13.

Purpose

Magnetic resonance images of biological media based on chemical exchange saturation transfer (CEST) show contrast that depends on chemical exchange between water and other protons. In addition, spin–lattice relaxation rates in the rotating frame (R1ρ) are also affected by exchange, especially at high fields, and can be exploited to provide novel, exchange-dependent contrast. Here, we evaluate and compare the factors that modulate the exchange contrast for these methods using simulations and experiments on simple, biologically relevant samples.

Methods

Simulations and experimental measurements at 9.4 T of rotating frame relaxation rate dispersion and CEST contrast were performed on solutions of macromolecules containing amide and hydroxyl exchanging protons.

Results

The simulations and experimental measurements confirm that both CEST and R1ρ measurements depend on similar exchange parameters, but they manifest themselves differently in their effects on contrast. CEST contrast may be larger in the slow and intermediate exchange regimes for protons with large resonant frequency offsets (e.g. > 2 ppm). Spin-locking techniques can produce larger contrast enhancement when resonant frequency offsets are small (< 2 ppm) and exchange is in the intermediate-to-fast regime. The image contrasts scale differently with field strength, exchange rate and concentration.

Conclusion

CEST and R1ρ measurements provide different and somewhat complementary information about exchange in tissues. Whereas CEST can depict exchange of protons with specific chemical shifts, appropriate R1ρ-dependent acquisitions can be employed to selectively portray protons of specific exchange rates.  相似文献   

14.
Polycrystalline CuIn1−xGaxTe2 bulk films were synthesized by reacting, in stoichiometric proportions, high purity Cu, In, Ga and Te in a vacuum sealed quartz ampoule. The phase structure and composition of the bulk films were analysed by X-ray diffraction and energy-dispersive X-ray analysis, respectively. The bulk samples, of p-type conductivity, are found to be near-stoichiometric, polycrystalline, with tetragonal chalcopyrite structure, predominantly oriented along a direction perpendicular to the (1 1 2) plane. Photoluminescence spectra were recorded at 7 K and 700 mW to characterize the defects and the structural quality. The main peak as a function of composition has been studied.  相似文献   

15.
Highly conducting films of p-type CuCrO2 are attractive as hole-injectors in oxide-based light emitters. In this paper, we report on the development of dry etch patterning of CuCrO2 thin films. The only plasma chemistry that provided some chemical enhancement was Cl2/Ar under inductively coupled plasma conditions. Etch rates of ∼500 Å min−1 were obtained at chuck voltages around −300 V and moderate source powers. In all cases, the etched surface morphologies were improved relative to un-etched control samples due to the smoothing effect of the physical component of the etching. The threshold ion energy for the onset of etching was determined to be 34 eV. Very low concentrations (≤1 at.%) of residual chlorine were detected on the etched surfaces but could be removed by simple water rinsing.  相似文献   

16.
Influence of gold- and carbon-coating on ToF-SIMS analysis of Cryptomeria japonica (Sugi) wood has been investigated to apply the samples after observing water distribution by cryo-scanning electron microscopy (cryo-SEM) or analyzing distribution of metal elements by SEM with energy dispersive X-ray spectrometer (SEM/EDX) to ToF-SIMS analysis to study the mechanism of heartwood formation of woody plants. The intensities of peaks at the m/z 285 ion in positive mode and the m/z 283 ion in negative mode from gold- and carbon-coated samples were compared with from those of non-coated samples. Those peaks were apparently attributable to ferruginol, a typical heartwood compounds in Sugi tree. From both gold- and non-coated samples, positive m/z 285 ions were generated. On the other hand, in negative mode, the intensity of m/z 283 ion was decreased after coating with gold. From carbon-coated samples, intensities of both positive m/z 285 ion and negative m/z 283 ion were decreased. These results suggest that the samples coated with gold for cryo-SEM could be applied to ToF-SIMS analysis directly to investigate the relation between water distribution and distribution of heartwood substances in heartwood-forming Sugi trees. However, non-coated samples should be used for SEM/EDX before analyzing by ToF-SIMS.  相似文献   

17.
The influences of Mn doping on the structural quality of the ZnxMn1−xO:N alloy films have been investigated by XRD. Chemical compositions of the samples (Zn and Mn content) and their valence states were determined by X-ray photoelectron spectrometry (XPS). Hall effect measurements versus temperature for ZnxMn1−xO:N samples have been designed and studied in detail. The ferromagnetic transitions happened at different TC should explain that the magnetic transition in field-cooled magnetization of Zn1−xMnxO:N films at low temperature is caused by the strong p-d exchange interactions besides magnetic transition at 46 K resulting from Mn oxide, and that the room temperature ferromagnetic signatures are attributed to the uncompensated spins at the surface of anti-ferromagnetic nano-crystal of Mn-related Zn(Mn)O.  相似文献   

18.
A low temperature (1100 °C) process of preparing F-doped SmFeAsO samples has been developed using SmF3 with nanometer scale as the source of fluorine. A series of the SmFeAsO1−xFx (= 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) samples have been prepared using the present method. Compared with previous reports, the present SmF3 is more effective to introduce F into SmFeAsO system in which a transition temperature of 39 K can be observed when = 0.05. The superconductivity is definitely enhanced with the increasing F-doping level. All the samples presented to be layered structure and the crystal particle size is about three times larger with sintering time increasing from 36 h to 48 h. Except for the nanometer scale of SmF3, the flux effect of SmF3 is recognized to be another reason for the decrease of the sintering temperature. Further more, a relatively large amount of SmF3 was also employed in the raw materials to introduce excessive F and this has induced higher Tc (55 K) in SmFeAsO0.8F0.2+δ system.  相似文献   

19.
A batch process for fabrication of GdBa2Cu3Oy pellets in air was developed. The samples were melt-processed using the cold-seeding method and as seeds Nd-123 thin films grown on MgO crystals. We used a self-made Gd-123 and Gd-211 powders mixed with 0.1 wt.% of Pt. Up to 1–1.5 kg of melt-grown Gd-123 bulks can be prepared in one process. XRD results confirmed that all the bulks are c-axis oriented. The superconducting and magnetic performance of the pellets is checked on several small test samples cut out at various standard positions within the bulk. The values are quite uniform and performance is similar to the oxygen-controlled melt-grown Gd-123 samples. The average trapped field at 77 K in the 24 mm diameter samples batch lies between 0.8 and 0.9 T. The maximum trapped field of 1 T at the sample surface was the highest value reported so far for Gd-123 single grains processed in air. The present results prove that a high-performance good-quality LREBa2Cu3Oy material can scale up from laboratory conditions to industrial production.  相似文献   

20.
In this paper, TaxC1−x coatings were deposited on 316L stainless steel (316L SS) by radio-frequency (RF) magnetron sputtering at various substrate temperatures (Ts) in order to improve its corrosion resistance and hemocompatibility. XRD results indicated that Ts could significantly change the microstructure of TaxC1−x coatings. When Ts was <150 °C, the TaxC1−x coatings were in amorphous condition, whereas when Ts was ≥150 °C, TaC phase was formed, exhibiting in the form of particulates with the crystallite sizes of about 15-25 nm (Ts = 300 °C). Atomic force microscope (AFM) results showed that with the increase of Ts, the root-mean-square (RMS) values of the TaxC1−x coatings decreased. The nano-indentation experiments indicated that the TaxC1−x coating deposited at 300 °C had a higher hardness and modulus. The scratch test results demonstrated that TaxC1−x coatings deposited above 150 °C exhibited good adhesion performance. Tribology tests results demonstrated that TaxC1−x coatings exhibited excellent wear resistance. The results of potentiodynamic polarization showed that the corrosion resistance of the 316L SS was improved significantly because of the deposited TaxC1−x coatings. The platelet adhesion test results indicated that the TaxC1−x coatings deposited at Ts of 150 °C and 300 °C possessed better hemocompatibility than the coating deposited at Ts of 25 °C. Additionally, the hemocompatibility of the TaxC1−x coating on the 316L SS was found to be influenced by its surface roughness, hydrophilicity and the surface energy.  相似文献   

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