共查询到10条相似文献,搜索用时 156 毫秒
1.
D. Demir Y. Şahin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):211-216
The effect of external magnetic field on the Kα
and Kβ X-ray production cross-sections and K shell fluorescence
yields for ferromagnetic elements Nd, Gd and Dy and paramagnetic elements Eu
and Ho have been measured at the excitation energy of 59.5 keV γ
-rays from 241Am radioactive source of strength 100 mCi in the
external magnetic field of intensities ±0.75 T. Furthermore,
IKβ /IKα intensity ratios for these elements have been
measured in the external magnetic field. The K X-rays from different targets
were detected using a high resolution Si(Li) semiconductor detector. For B = 0, the measured K X-ray production cross-sections,
K shell fluorescence
yields and the IKβ /IKα intensity ratios were compared
with the experimental and theoretical data in literature. The results have
shown that the fluorescence parameters as photoionization cross section,
fluorescence yield, radiation rates and spectral linewidth can change when
the irradiation is conducted in a magnetic field. 相似文献
2.
K. S. Mann K. S. Kahlon N. Singh K. L. Allawadhi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):455-456
The total M shell relative photoionization
cross-sections for Au, Pb, Th and U have been measured in the energy region
6–12 keV. External conversion K X-rays of suitable elements has been employed
as incident photons to photo ionize the total M shell of elements under
investigation. The method provides relative cross-sections therefore does
not make use of theoretically calculated average M shell fluorescence yields
which involve uncertainties of the order of 20%. No evidence of deviation
from calculated values of cross-sections have been observed within
experimental errors for all incident photon energies. 相似文献
3.
Two simple, sensitive and specific fluorimetric methods have been developed for the determination of some sulphur containing
compounds namely, Acetylcysteine (Ac), Carbocisteine (Cc) and Thioctic acid (Th) using terbium Tb+3 and uranium U+3 ions as fluorescent probes. The proposed methods involve the formation of a ternary complex with Tb+3 in presence of Tris-buffer method (I) and a binary complex with aqueous uranyl acetate solution method (II). The fluorescence
quenching of Tb+3 at 510, 488 and 540 nm (λex 250, 241 and 268 nm) and of uranyl acetate at 512 nm (λex 240 nm) due to the complex formation was quantitatively measured for Ac, Cc and Th, respectively. The reaction conditions
and the fluorescence spectral properties of the complexes have been investigated. Under the described conditions, the proposed
methods were applicable over the concentration range (0.2–2.5 μg ml−1), (1–4 μg ml−1) and (0.5–3.5 μg ml−1) with mean percentage recoveries 99.74±0.36, 99.70±0.52 and 99.43±0.23 for method (I) and (0.5–6 μg ml−1), (0.5–5 μg ml−1), and (1–6 μg ml−1) with mean percentage recoveries 99.38±0.20, 99.82±0.28 and 99.93±0.32 for method (II), for the three cited drugs, respectively.
The proposed methods were successfully applied for the determination of the studied compounds in bulk powders and in pharmaceutical
formulations, as well as in presence of their related substances. The results obtained were found to be in agree statistically
with those obtained by official and reported ones. The two methods were validated according to USP guidelines and also assessed
by applying the standard addition technique. 相似文献
4.
E. Tıraşoğlu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,37(2):177-180
M4,5 subshells average fluorescence yields (ϖM4,5) have been determined for thorium and uranium using M4,5 X-ray production cross-sections at 5.96 keV incident photon energy. The measurements have been performed using a 55Fe annular source and an Ultra-LEGe detector. The present values are compared with calculated theoretical values and theoretical
average M shell fluorescence yields (ϖM). Fair agreement (to within 22–27%) is typically obtained between present average fluorescence yields (ϖM4,5) and calculated theoretical values. 相似文献
5.
《The European Physical Journal C - Particles and Fields》2007,52(3):543-552
In this paper a search for associated charm production both in neutral and charged current ν-nucleus interactions is presented.
The improvement of automatic scanning systems in the CHORUS experiment allows an efficient search to be performed in emulsion
for short-lived particles. Hence a search for rare processes, like the associated charm production, becomes possible through
the observation of the double charm-decay topology with a very low background. About 130000 ν interactions located in the
emulsion target have been analysed. Three events with two charm decays have been observed in the neutral-current sample with
an estimated background of 0.18±0.05. The relative rate of the associated charm cross-section in deep inelastic ν interactions,
σ(cc̄ν)/σNC
DIS=(3.62+2.95
-2.42(stat)±0.54(syst))×10-3 has been measured. One event with two charm decays has been observed in charged-current νμ interactions with an estimated background of 0.18±0.06 and the upper limit on associated charm production in charged-current
interactions at 90% C.L. has been found to be σ(cc̄μ-)/σCC<9.69×10-4. 相似文献
6.
In view of the discrepancies between the values available in the literature for the photophysical parameters of tetraazaporphin
in solutions, we measured its quantum yield and duration of fluorescence in a number of solvents. It has been found that alcohols
(isobutanol and isopropanol) quench the fluorescence appreciably. For a solution in toluene — a stable chemically inactive
and low-polar solvent — the measured quantum yield of the fluorescence of tetraazaporphin is equal to 0.180 ± 0.015 and its
duration is 3.4 ± 0.1 nsec.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 5, pp. 697–699, September–October, 2005. 相似文献
7.
《The European Physical Journal C - Particles and Fields》2007,50(2):315-328
The inclusive production cross sections of the strange vector mesons K*0, K̄*0, and φ have been measured in interactions of 920 GeV protons with C, Ti, and W targets with the HERA-B detector at the HERA
storage ring. Differential cross sections as a function of rapidity and transverse momentum have been measured in the central
rapidity region and for transverse momenta up to pT = 3.5 GeV/c. The atomic number dependence is parametrised as σpA=σpN*Aα, where σpN is the proton–nucleon cross section. Within the phase space accessible, α(K*0)=0.86±0.03, α(K̄*0)=0.87±0.03, and α(φ)=0.96±0.02. The total proton–nucleon cross sections, determined by extrapolating the differential measurements
to full phase space, are σpN→K*0=(5.06±0.54) mb, σpN→K̄*0=(4.02±0.45) mb, and σpN→φ=(1.17±0.11) mb. For all resonances the Cronin effect is observed; compared to the measurements of Cronin et al. for K± mesons, the measured values of α for φ mesons coincide with those of K+ mesons for all transverse momenta, while the enhancement for K*0/K̄*0 mesons is smaller. 相似文献
8.
In an effort to resolve the existing discrepancy between experiment and theory, the cross-sections for the production ofL
l,L
α
,L
β
andL
γ
groups ofL-shell X-rays of Ho by photons of nine energies in the range 10–40 keV have been measured using an improved version of annular
source double reflection geometrical set-up. Contrary to the earlier findings of Garget al that the measured values of the cross-sections are consistently higher than those calculated theoretically, the present results
do not confirm this. The plausible deficiencies in the experiments of Garget al are pointed out and possible remedies to overcome them are suggested. It is concluded that the higher values obtained by
Garget al are probably due to systematic errors in their method of measurement. 相似文献
9.
J.L. de la Peña M.I. Pech-Canul 《Applied Physics A: Materials Science & Processing》2008,91(3):545-550
The wetting behavior of Al–Si–Mg alloys on Si3N4/Si substrates has been investigated using the sessile drop technique. Based on a Taguchi experiment design, the effect of
the following processing parameters on the contact angle (θ) and surface tension (σLV) was studied: processing time and temperature, atmosphere (Ar and N2), substrate surface condition (with and without a silicon wafer), as well as the Mg and Si contents in the aluminium alloy.
In nitrogen, non-wetting conditions prevail during the isothermal events while in argon a remarkable non-wetting to wetting
transition leads to contact angles θ as low as 11±3° and a liquid surface tension σLV of 33± 10×10-5 kJ/m2. According to the multiple analysis of variance (Manova), the optimum conditions for minimizing the values of θ and σLV are as follows: temperature of 1100 °C, processing time of 90 min, argon atmosphere, no use of a silicon wafer, and the use
of the Al-18% Mg-1% Si alloy. A verification test conducted under the optimized conditions resulted in a contact angle of
θ=9±3° and a surface tension of σLV=29± 9×10-5 kJ/m2, both indicative of excellent wetting.
PACS 68.03.Cd; 81.05.Bx; 68.08.Bc; 05.70.-a; 61.10.Nz 相似文献
10.
The quantum yield, ΦΔ, of singlet oxygen generation under two-photon excitation has been determined for a fluorene derivative. A photochemical
method was developed using 1,3-diphenylisobenzofuran (DPBF), a chemical quencher of 1O2, and 2-(9,9-didecyl-7-nitrofluoren-2-yl)benzothiazole (1) as a two-photon photosensitizer (PS). The photochemical kinetics of the quencher was measured by two different fluorescence
methods. Fluorene 1 exhibited relatively high singlet oxygen quantum yield, ΦΔ ≈ 0.4 ± 0.1, and had a two-photon absorption cross-section of 28 ± 5 GM. Thus, 1 may have potential for use as a two-photon PS in the near-IR spectral region for biomedical applications. 相似文献