共查询到20条相似文献,搜索用时 31 毫秒
1.
A. K. Mahur Rajesh Kumar D. Sengupta Rajendra Prasad 《Indian Journal of Physics》2009,83(7):1011-1018
Chhatrapur beach placer deposit, situated in a part of the eastern coast of Orissa, is a newly discovered high natural background
radiation area (HBRA) in India. The sand samples containing heavy minerals, were collected from Chhatrapur region by the grab
sampling method at an interval of ∼1 Km. Radon exhalation rates were measured by “Sealed Can Technique” using LR-115 type
type II in the sand samples containing heavy minerals collected from the beach. Radon activity is found to vary from 1177.1
to 4551.4 Bq m-3 whereas the radon exhalation rate varies from 423.2 to 1636.3 mBq m−2h−1 with an average value of 763.9 mBq m−2h−1. Effective dose equivalent in sand samples estimated from exhalation rate varies from 49.9 to 193.0 μSv y−1 with an average value of 90.1 μSv y−1. From the activity concentration of 238U, 232Th and 40K computed radium equivalent is found to vary from 864.0 to 11471.5 Bq kg−1 with an average value of 3729.0 Bq kg−1. External hazard index, Hex range from 2.3 to 31.0 with a mean value of 10.1, which is quite high. This value supports the conclusion based on high mean
absorbed gamma dose rate in air due to the naturally occurring radionuclides as 1627.5 nGy h−1. A positive correlation has been found between U concentration and radon exhalation rate in the sand samples. The use of
sand as construction material may pose a radiation risk to ambient environment.
相似文献
2.
Hosseini M Ganjali MR Tavakoli M Norouzi P Faridbod F Goldooz H Badiei A 《Journal of fluorescence》2011,21(4):1509-1513
A novel and simple fluorescence enhancement method for selective pyrophosphate(PPi) sensing was proposed based on a 1:1 metal
complex formation between bis(8-hydroxy quinoline-5-solphonat) chloride aluminum(III) (Al(QS)2Cl), (L) and PPi in aqueous solution. The linear response range covers a concentration range of 1.6 × 10−7 to 1.0 × 10−5 mol/L of PPi and the detection limit of 2.3 × 10−8 mol/L. The association constant of L-PPi complex was calculated 2.6 × 105 L/mol. L was found to show selectively and sensitively fluorescence enhancement toward PPi over than I3-, NO3-, CN−, CO32−, Br−, Cl−, F−, H2PO4− and SO42−, which was attributed to higher stability of inorganic complex between pyrophosphate and L. 相似文献
3.
Deok Kyu Kim Kyeong Min Kim Choon Bae Park 《Applied Physics A: Materials Science & Processing》2010,98(4):913-917
A p-type ZnO thin film was prepared using arsenic diffusion via the ampoule-tube method. This was followed by fabrication
of a ZnO p–n homojunction using n-type ZnO and characterization of the device properties. The ZnO thin film exhibited p-type
characteristics, with a resistivity of 2.19×10−3 Ω cm, a carrier concentration of 1.73×1020/cm3, and a mobility of 26.7 cm2/V s. Secondary ion mass spectrometer analysis confirmed that in- and out-diffusion occurred simultaneously from the external
As source and the GaAs substrate. The device exhibited the rectification characteristics of a typical p–n junction; the forward
voltage at 20 mA was approximately 5.5 V. The reverse-bias leakage current was very low—0.1 mA for −10 V; the breakdown voltage
was −11 V. The ampoule-tube method for fabricating p-type ZnO thin films may be useful in producing ultraviolet ZnO LEDs and
other ZnO-based devices. 相似文献
4.
Encapsulation of iron nanoparticles in alginate biopolymer for trichloroethylene remediation 总被引:2,自引:0,他引:2
Achintya N. Bezbaruah Sai Sharanya Shanbhogue Senay Simsek Eakalak Khan 《Journal of nanoparticle research》2011,13(12):6673-6681
Nanoscale zero-valent iron (NZVI) particles (10–90 nm) were encapsulated in biodegradable calcium-alginate capsules for the
first time for application in environmental remediation. Encapsulation is expected to offers distinct advances over entrapment.
Trichloroethylene (TCE) degradation was 89–91% in 2 h, and the reaction followed pseudo first order kinetics for encapsulated
NZVI systems with an observed reaction rate constant (k
obs) of 1.92–3.23 × 10−2 min−1 and a surface normalized reaction rate constant (k
sa) of 1.02–1.72 × 10−3 L m−2 min−1. TCE degradation reaction rates for encapsulated and bare NZVI were similar indicating no adverse affects of encapsulation
on degradation kinetics. The shelf-life of encapsulated NZVI was found to be four months with little decrease in TCE removal
efficiency. 相似文献
5.
H. Ryssel H. Iberl M. Bleier G. Prinke K. Haberger H. Kranz 《Applied Physics A: Materials Science & Processing》1981,24(3):197-200
The diffusion behavior of implanted arsenic in polycrystalline silicon was investigated, using backscattering and electrical
measurements. The diffusion coefficient isD=8.5×10−3 exp (−2.74/kT) for polycrystalline silicon deposited on freshly-etched silicon andD=1.66 exp (−3.22/kT) for the deposition on silicon having natural oxide. At the interface to the single-crystalline silicon,
a pile-up of arsenic occurs, which depends also on the surface treatment prior to the deposition of the polycrystalline silicon. 相似文献
6.
Chemiluminescence (CL) of the reaction system tetracycline–H2O2–Fe(II)/(III)–Eu(III) was used for the determination of tetracycline hydrochloride in water, pharmaceutical preparations,
and honey. The CL spectrum registered for this system shows emission bands typical of Eu(III) ions, with a maximum at λ ∼ 600 nm,
corresponding to the electronic transitions of 5D0 → 7F1 and 5D0 → 7F2. A strong chemiluminescence intensity characteristic of europium(III) ions in the system tetracycline–H2O2–Fe(II)/(III)–Eu(III), as contrasted to the emission of the system tetracycline–H2O2–Fe(II)/(III) without Eu(III), proves that the Eu(III) ion plays the role of a chemiluminescence sensitizer, accompanying
tetracycline oxidation in the Fenton system (H2O2–Fe(II)/(III)). A linear dependence was observed for the integrated CL light intensity on the tetracycline concentration in
the range of 2 × 10−7 to 3 × 10−5 mol l−1 with the detection limit of 5 × 10−8 mol l−1 in aqueous solution. 相似文献
7.
Supercapacitor devices using porous silicon electrodes 总被引:1,自引:0,他引:1
Electrical double layer (EDL) supercapacitors have been constructed using gold coated porous silicon (PSi) electrodes in a
0.25 M TEABF4/PC solution. As a comparison with the PSi, graphite paper, carbon cloth and ITO on glass electrodes have also been tested
using the same electrolyte. The capacitors have been characterised using a.c. impedance spectroscopy and cyclic voltammetry
(normal staircase mode). Devices using PSi electrodes showed a capacitance of approximately 0.2 mF cm−2 (equivalent to 5 mF g−1). In comparison, devices based on ITO on glass electrodes had a capacitance of 0.76 mF cm−2. Those based on graphite-paper electrodes gave 10 mF cm−2 (equivalent to 131 mF g−1) and those using carbon cloth gave 600 mF cm−2 (equivalent to 35 F g−1).
Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999. 相似文献
8.
Moshe Carmeli John G. Hartnett Firmin J. Oliveira 《International Journal of Theoretical Physics》2006,45(6):1074-1078
The anomalous acceleration of Pioneer 10 and 11 spacecrafts of (8.74± 1.33) × 10−8 cm s−2 fits with a theoretical prediction of a minimal acceleration in nature of 7.61× 10−8 cm s−2. 相似文献
9.
Three sensitive and selective new alternatives for fluorometric determination of cerium(III) are described in this study.
Ce(III) is highly fluorescent in sodium pyrophosphate, sodium trimetaphosphate, and sodium tetrametaphosphate solutions. For
these reagents, the maximum excitation/emission wavelengths are 300/350, 297/340, and 299/352 nm, respectively. Maximum fluorescence
intensities are obtained by irradiating Ce(III) dissolved in 0.033 g L−1 sodium pyrophosphate, 41.4 g L−1 sodium trimetaphosphate, and 0.96 g L−1 sodium tetrametaphosphate at room temperature. The fluorescence intensities are linear over the range 0.001–30, 0.001–75,
and 0.001–70 μg ml−1. The detection limits are calculated as 9.5 × 10−3, 1.1/10−3, and 3.8 × 10-3 μg ml−1 Ce(III), respectively. The relative standard deviations for 15/0.05 Μg ml−1 Ce(III) are 1.1/1.2, 1/1.1, and 1.2/1.3%, respectively. Quenching effects of other lanthanides and some inorganic anions
were investigated. The methods have been applied to rare earth mixtures with a good accuracy. 相似文献
10.
Ganesh Prasad Yogesh Prasad G. S. Gusain Manjari Badoni J. M. S. Rana R. C. Ramola 《Indian Journal of Physics》2009,83(6):887-892
Radon was measured in soil-gas and groundwater in the Budhakedar area of Tehri Garhwal, India in summer and winter to obtain
the seasonal variation and its correlation with radon exhalation rate. The environmental surface gamma dose rate was also
measured in the same area. The radon exhalation rate in the soil sample collected from different geological unit of Budhakedar
area was measured using plastic track detector (LR-115 type II) technique. The variation in the radon concentration in soil-gas
was found to vary from 1098 to 31,776 Bq.m−3 with an average of 7456 Bq.m−3 in summer season and 3501 to 42883 Bq.m−3 with an average of 17148 Bq.m−3 in winter season. In groundwater, it was found to vary from 8 to 3047 Bq.l−1 with an average value 510 Bq.l−1 in summer and 26 to 2311 Bq.l−1 with an average value 433 Bq.L−1 in winter. Surface gamma dose rate in the study area varied from 32.4 to 83.6 μR.h−1 with an overall mean of 58.7 μ-R.h−1 in summer and 34.6 to 79.3 μR.h−1 with an average value 58.2 μR.h−1 in winter. Radon exhalation rate from collected soil samples was found to vary from 0.1 × 10−5 to 5.7 × 10−5 Bq.kg−1.h−1 with an average of 1.5 × 10−5 Bq.kg−1.h−1 in summer season and 1.7 × 10−5 to 9.6 × 10−5 Bq.kg−1.h−1 with an average of 5.5 × 10−5 Bq.kg−1.h−1. A weak negative correlation was observed between radon exhalation rate from soil and radon concentration in the soil. Radon
exhalation rate from the soil was also not found to be correlated with the gamma dose rate, while it shows a positive correlation
with radon concentration in water in summer season. Inter-correlations among various parameters are discussed in detail.
相似文献
11.
Pushpa Khare 《Pramana》1999,53(6):1027-1032
We have tried to understand the recent observations related to metallicity in Ly-α forest clouds in the framework of the two
component model. The model consists of mini-halos having circular velocities smaller than ∼ 55 km s−1, with no star formation and galactic halos with higher circular velocities ≤ 250 km s−1, having clouds, star formation and consequent metal enrichment. We find that even if the mini-halos were chemically enriched
by an earlier generation of stars, to have [C/H] ≃ −2.5, the number of C IV lines with column density >1012 cm−2, contributed by the mini-halos, at the redshift of 3, would be only about 10% of the total number of lines, for a chemical
enrichment rate of (1 + z)−3 in the galaxies. Recently reported absence of heavy element lines associated with most of the Ly-α lines with HI column density
between 1013.5 cm−2 and 1014 cm−2 by Lu et al [13], if correct, gives an upper limit on [C/H]= −3.7, not only in the mini-halos, but also in the outer parts of galactic
halos. However, the mean value of 7×10−3 for the column density ratio of C IV and HI, determined by Cowie and Songaila (1998) for low Ly-α optical depths, implies
an abundance of [C/H]= −2.5 in mini-halos as well as most of the region in galactic halos. The redshift and column density
distribution of C IV has been shown to be in reasonable agreement with the observations. 相似文献
12.
P.?Madejczyk A.?Piotrowski K.?K?os W.?Gawron J.?Rutkowski A.?Rogalski 《Opto-Electronics Review》2010,18(3):271-276
The acceptor doping of mercury cadmium telluride (HgCdTe) layers grown by MOCVD are investigated. (111)HgCdTe layers were
grown on (100)GaAs substrates at 350°C using horizontal reactor and interdiffused multilayer process (IMP). TDMAAs and AsH3
were alternatively used as effective p-type doping precursors. Incorporation and activation rates of arsenic have been studied.
Over a wide range of Hg1−xCdxTe compositions (0.17 < x < 0.4), arsenic doping concentration in the range from 5×1015 cm−3 to 5×1017 cm−3 was obtained without postgrowth annealing. The electrical and chemical properties of epitaxial layers are specified by measurements
of SIMS profiles, Hall effect and minority carrier lifetimes. It is confirmed that the Auger-7 mechanism has decisive influence
on carrier lifetime in p-type HgCdTe epilayers. 相似文献
13.
M. Takai P. H. Tsien S. C. Tsou D. Röschenthaler M. Ramin H. Ryssel I. Ruge 《Applied Physics A: Materials Science & Processing》1980,22(2):129-136
CW CO2-laser annealing of arsenic implanted silicon was investigated in comparison with thermal annealing. Ion channeling, ellipsometry,
and Hall effect measurements were performed to characterize the annealed layers and a correlation among the different methods
was made. The laser annealing was done with power densities of 100 to 640 W cm−2 for 1 to 20 s. It was found that the lattice disorder produced during implantation can be completely annealed out by laser
annealing with a power density of 500 W cm−2 and the arsenic atoms are brought on lattice sites up to 96±2%. The maximum sheet carrier concentration of 6×1015 cm−2 was obtained for 1×1016 cm−2 implantation after laser annealing, which was up to 33% higher than that after thermal annealing at 600 to 900°C for 30 min. 相似文献
14.
Chan y Díaz E. Duarte-Moller A. Camacho Juan M. Castro-Rodríguez R. 《Applied Physics A: Materials Science & Processing》2012,106(3):619-624
SnO2 thin films have been deposited on glass substrates by pulsed Nd:YAG laser at different oxygen pressures, and the effects
of oxygen pressure on the physical properties of SnO2 films have been investigated. The films were deposited at substrate temperature of 500°C in oxygen partial pressure between
5.0 and 125 mTorr. The thin films deposited between 5.0 to 50 mTorr showed evidence of diffraction peaks, but increasing the
oxygen pressure up to 100 mTorr, three diffraction peaks (110), (101) and (211) were observed containing the SnO2 tetragonal structure. The electrical resistivity was very sensitive to the oxygen pressure. At 100 mTorr the films showed
electrical resistivity of 4×10−2 Ω cm, free carrier density of 1.03×1019 cm−3, mobility of 10.26 cm2 V−1 s−1 with average visible transmittance of ∼87%, and optical band gap of 3.6 eV. 相似文献
15.
6-Hydroxy chromone-3-carbaldehyde-(4′-hydroxy) benzoyl hydrazone (L) and its Ln (III) complexes, [Ln = La, Nd, Eu and Tb]
have been prepared and characterized on the basis of elemental analyses, molar conductivities, mass spectra, 1H NMR, thermogravimety/differential thermal analysis (TG-DTA), UV-vis spectra, fluorescence spectra and IR spectra. The formula
of the complex is [Ln L·(NO3)2]·NO3. Spectrometric titration, ethidium bromide displacement experiments and viscosity measurements indicate that Eu (III) complex
bind with calf-thymus DNA, presumably via an intercalation mechanism. The intrinsic binding constant of Eu (III) with DNA
was 2.48 × 105 M−1 through fluorescence titration data. 相似文献
16.
Non-aqueous polymer gel electrolytes containing trifluoromethanesulfonic acid (HCF3SO3) and polyethylene oxide (PEO) as the gelling polymer has been studied. The increase in conductivity observed with the addition
of PEO to liquid electrolytes has been explained to be due to the breaking of ion aggregates present in electrolytes at higher
acid concentrations. The increase in free H+ ion concentration upon breaking of ion aggregates has also been observed in pH measurements and viscosity of gel electrolytes
has been found to increase with PEO addition. Polymer gel electrolytes containing dimethylacetamide (DMA) have σ ∼ 10−2 S/cm at room temperature and are stable over −50 to 125 °C range of temperature. Gels based on propylene carbonate (PC) and
ethylene carbonate (EC) are stable in the −50 to 40 °C temperature range and loose their gelling nature above 40 °C. 相似文献
17.
E. G. Guk M. E. Levinshtein V. A. Marikhin L. P. Myasnikova 《Physics of the Solid State》1998,40(6):1062-1065
Changes in the optical properties of conducting polydiacetylene THD (poly-1,1,6,6-tetraphenylhexadiindiamine) brought on by
doping are investigated for the first time. Spectral dependences of the extinction coefficients were studied in the range
400–25 000 cm−1 both for the undoped polymer (σ<10−9 S/cm) and at various doping levels (up to σ∼5×10−3 S/cm). The results obtained attest to the appearance of high carrier concentrations in polydiacetylene THD with conductivities
σ⩾10−4 S/cm. The relatively low observed macroscopic conductivity is explained by the complex hierarchy of structural formations
that are intrinsic to polymers. The results obtained are compared with the corresponding data for conducting polyacetylene.
Fiz. Tverd. Tela (St. Petersburg) 40, 1162–1166 (June 1998) 相似文献
18.
Serge Zhuiykov 《Ionics》2009,15(4):507-512
In situ Fourier transform spectroscopy (FTIR) was used to study interactions of nanostructured ruthenium oxide (RuO2) thin-film sensing electrode with O2 at room temperature. RuO2 nanostructures were pretreated at 1,000 °C for 1 h in order to obtain good crystallinity of amorphous RuO2 nanoparticles. Morphology and properties of nanostructured RuO2 were characterized by X-ray diffraction, thermo-gravimetric/differential thermal analysis, scanning electron microscopy,
and FTIR. It was shown that pretreated RuO2 is quite active for O2
−, O2
2−, and O2− adsorption with clear 722 cm−1 band for superoxide ions (O2
−) adsorption for the different oxygen concentrations. The results of in situ FTIR measurements revealed that the active sites
for oxygen adsorption are not limited to the triple boundaries, but extended to surfaces of RuO2 electrodes. Fundamental vibration frequencies of ruthenium–oxygen bond at a temperature of 23 °C as well as region above
fundamental frequencies for the nanostructured RuO2 were identified. 相似文献
19.
Non-aqueous polymer gel electrolytes containing trifluoromethanesulfonic acid (HCF3SO3) and polyethylene oxide (PEO) as the gelling polymer has been studied. The increase in conductivity observed with the addition
of PEO to liquid electrolytes has been explained to be due to the breaking of ion aggregates present in electrolytes at higher
acid concentrations. The increase in free H+ ion concentration upon breaking of ion aggregates has also been observed in pH measurements and viscosity of gel electrolytes
has been found to increase with PEO addition. Polymer gel electrolytes containing dimethylacetamide (DMA) have σ ∼ 10−2 S/cm at room temperature and are stable over −50 to 125 °C range of temperature. Gels based on propylene carbonate (PC) and
ethylene carbonate (EC) are stable in the −50 to 40 °C temperature range and loose their gelling nature above 40 °C. 相似文献
20.
Yoshio Kobayashi Hidekazu Kakinuma Daisuke Nagao Yasuo Ando Terunobu Miyazaki Mikio Konno 《Journal of nanoparticle research》2009,11(7):1787-1794
This article describes a method for silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone)
(PVP) as a stabilizer. The Co–Pt nanoparticles were prepared in an aqueous solution at 25–80 °C from CoCl2 (3.0 × 10−4 M), H2PtCl6 (3.0 × 10−4 M), PVP (0–10 g/L), and NaBH4 (4.8 × 10−3–2.4 × 10−2 M). The silica coating was performed for the Co–Pt nanoparticle colloid containing the PVP ([Co] = [Pt] = 3.0 × 10−5 M) at 25 °C in (1/4) (v/v) water/ethanol solution with tetraethoxyorthosilicate (TEOS) (7.2 × 10−5–7.2 × 10−3 M) and ammonia (0.1–1.0 M). Silica particles, which had an average size of 43 nm and contained multiple cores of Co–Pt nanoparticles
with a size of ca. 8 nm, were produced at 1.4 × 10−3 M TEOS and 0.5 M ammonia after the preparation of Co–Pt nanoparticles at 80 °C, 5 g/L PVP, and 2.4 × 10−2 M NaBH4. Their core particles were fcc Co–Pt alloy crystallites. Their saturation magnetization was 2.0-emu/g sample, and their coercive
field was 12 Oe. 相似文献