共查询到20条相似文献,搜索用时 15 毫秒
1.
Statistical control charts are presented for the evaluation of time series radiation counter data from flow cells used for
monitoring of low levels of 99TcO4− in environmental solutions. Control chart methods consisted of the 3-sigma (3σ) chart, the cumulative sum (CUSUM) chart, and the exponentially weighted moving average (EWMA) chart. Each method involves
a control limit based on the detector background which constitutes the detection limit. Both the CUSUM and EWMA charts are
suitable to detect and estimate sample concentration requiring less solution volume than when using a 3σ control chart. Data presented here indicate that the overall accuracy and precision of the CUSUM method is the best. 相似文献
2.
A. Cesana A. Nava A. Teatini T. Tenconi M. Terrani S. Terrani 《Journal of Radioanalytical and Nuclear Chemistry》1978,42(2):435-445
A method of estimating total body calcium and sodium in rats by in vivo neutron activation analysis is described. The subjects
were exposed to an integrated flux of about 1.6·1011 thermal neutrons and activity was determined by counting with a 3″×3″ NaI(Tl) detector. The growth of the subjects was followed
for about 75 days. The values of total body concentrations obtained are 0.83–0.90% for Ca and 0.128% for Na. Consideration
is given to the accuracy attainable and to the effects on the blood and the hematopoietic tissues of the radiation doses imparted. 相似文献
3.
K. D. Ianakiev J. M. Goda T. R. Hill C. E. Moss J. J. Ong M. T. Paffett R. F. Parker M. T. Swinhoe 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(2):657-661
We report our developments of the next generation of uranium enrichment monitoring technology for gas centrifuge enrichment
plants (GCEPs). The main challenge presented by current technology is the need for periodic replacement of the short half-life
(1.27 year) 109Cd transmission source. We report on a transmission source at the 22.1 keV K-edge of ruthenium based on an X-ray tube with
a “notch” filter. As part of the design we have modeled the NaI detector passive shielding with the MCNP code. Some preliminary
results from experiments and modeling will be presented. 相似文献
4.
Gregory D. Schilling Jacob T. Shelley James H. Barnes Roger P. Sperline M. Bonner Denton Charles J. Barinaga David W. Koppenaal Gary M. Hieftje 《Journal of the American Society for Mass Spectrometry》2010,21(1):97-103
An ambient desorption/ionization (ADI) source, known as the flowing atmospheric pressure afterglow (FAPA), has been coupled
to a Mattauch-Herzog mass spectrograph (MHMS) equipped with a focal plane camera (FPC) array detector. The FAPA ionization
source enables direct mass spectral analysis of solids, liquids, and gases through either positive or negative ionization
modes. In either case, spectra are generally simple with dominant peaks being the molecular ions or protonated molecular ions.
Use of the FAPA source with the MHMS allows the FPC detector to be characterized for the determination of molecular species,
whereas previously only atomic mass spectrometry (MS) has been demonstrated. Furthermore, the FPC is shown to be sensitive
to negative ions without the need to change any detector parameters. The analysis of solid, liquid, and gaseous samples through
positive and negative ionization is demonstrated with detection limits (1–25 fmol/s, ∼0. 3–10 pg of analyte per mL of helium)
surpassing those obtained with the FAPA source coupled to a time-of-flight mass analyzer. 相似文献
5.
D. V. Kuznetsov S. A. Andreev A. K. Tashmukhamedova 《Chemistry of Natural Compounds》2006,42(5):515-516
Diazonium salts were prepared by diazotization of 4′-amino-, 4′,4″-, and 4′,5″-diaminodibenzo-18-crown-6. Their coupling products
with kojic acid (5-hydroxy-2-hydroxymethyl-γ-pyrone) were synthesized for the first time: 4′-(6-aza-5-hydroxy-2-hydroxymethyl-γ-pyronyl)-, 4′,4″-di-(6-aza-5-hydroxy-2-hydroxymethyl-γ-pyronyl)-, and 4′,5″-di-(6-aza-5-hydroxy-2-hydroxymethyl-γ-pyronyl)-dibenzo-18-crown-6.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 415–416, September–October, 2006. 相似文献
6.
R. M. Ward S. R. F. Biegalski D. A. Haas W. Hennig 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(3):693-697
The monitoring of atmospheric radioxenon to ensure compliance with the Comprehensive Nuclear Test Ban Treaty (CTBT) has driven
the development of improved detectors for measuring xenon, including the development of a phoswich detector. This detector
uses only one PMT to detect β–γ coincidence, thus greatly reducing the bulk and electronics of the detector in comparison
to the ARSA-type detector. In this experiment, 135Xe was produced through neutron activation and a phoswich detector was used to attain spectra from the gas. These results
were compared to similar results from an ARSA-type β–γ coincidence spectrum. The spectral characteristics and resolution were
compared for the coincidence and beta spectra. Using these metrics, the overall performance of the phoswich detector for β–γ
coincidence of radioxenon was evaluated. 相似文献
7.
A. D. Grebenyuk V. I. Vinogradova A. K. Tashmukhamedova 《Chemistry of Natural Compounds》2006,42(5):585-587
New derivatives of dibenzo-24-crown-8-dicarboxylic acid diamide with salsoline, salsolidine, and anabasine moieties were prepared
by condensation of the alkaloids with 4′,4″(5″)-dibenzo-24-crown-8-dicarboxylic acid dichloride.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 471–473, September–October, 2006. 相似文献
8.
Sz. Vass B. Vorsatz E. Szabó E. Kelen B. Keszei S. Cseh S. Saly 《Journal of Radioanalytical and Nuclear Chemistry》1971,8(2):325-334
A non-destructive simultaneous method has been developed for the rapid determination of Al, Si and K in WO3 powders and W metal powders. The samples were activated by 14 MeV neutrons and the radioactive isotopes identified by their
γ-ray spectra with a 3″×3″ NaI(Tl) detector. Quantitative analysis was carried out by measuring the full energy peak areas.
The determined concentrations of Al, Si and K were above 100, 100 and 500 ppm, the sensitivities being about 20, 10 and 100
ppm, respectively. 相似文献
9.
Claudia Lar Gheorghe-Doru Roiban Romina Mariana Crăsneanu Ilişca Mihalca Elena Bogdan Anamaria Terec Ion Grosu 《Central European Journal of Chemistry》2011,9(2):218-223
The synthesis and photophysical properties of several 6,6″ symmetrically substituted 4′-aryl-2,2′:6′,2″-terpyridine derivatives
are reported herein. The UV-Vis spectra in acetonitrile as well as in dichloromethane show two intense bands in the UV areas
252–262 nm and 275–290 nm while the fluorescence emission spectra are only slightly influenced by chemical derivatization. 相似文献
10.
Euchrenone a2 (7) isolated from the roots ofEuchresta japonica has been synthesised from 3-prenylphloroacetophenone (1) by other workers. We carried out its cyclodehydrogenation with dichloro dicyano quinone (DDQ) to obtain 6-acetyl-5,7-dihydroxy-2,2-dimethylchromene
(2) which was ethoxymethylated in the 7-position to give 6-acetyl-7-ethoxymethoxy-5-hydroxychromene (3). Chalcone condensation of3 and 4-ethoxymethoxy-3-C-prenylbenzaldehyde (4) gave 4,6′-bisethoxymethoxy-2′-hydroxy-6″, 6″-dimethyl-3-C-prenylpyrano (2″, 3″–4,3) chalcone (5) which cyclised with methanolic sodium acetate to give protected 5,4′-bisethoxymethoxy-6″, 6″-dimethyl-3′-C-prenylpyrano (2″, 3″–7,8) flavanone (6). Deprotection of6 with 4% methanolic HCl yielded (7) with melting point and spectral data identical to that of the natural compound. 相似文献
11.
4′,4″(5″)-(Dibenzo-18-crown-6)diarylacetohydroxamic acids were obtained by the reaction of DB18C-6 with β-nitrostyrenes under
the influence of polyphosphoric acid.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 838–840, June, 2006. 相似文献
12.
The absorption spectra in dilute dichloromethane solution at 300 K of four Oligotiophenes (OT), namely 2,2′:5′,2″-Terthiophene,
2,2′:5′,2″:5″,2″′-Quaterthiophene, 4,4″′-Didodecyl-2,2′:5′,2″:5″,2″′-quaterthiophene and 5,5′′′′′-Dihexyl-2,2′:5′,2′′:5′′,2′′′:5′′′,2′′′′:5′′′′,2′′′′′-sexithiophene,
have been studied both experimentally and theoretically by using a combination of molecular dynamics simulations, time-dependent
density functional theory (TD-DFT) and perturbed matrix method calculations. A deep analysis of the theoretical results, affected
by a systematic although not dramatic underestimation of the absorption maxima due to the well-documented TD-DFT limitations,
clearly indicates that both the environmental (solvent) and thermal effects significantly alter the Oligotiophenes photophysical
properties mainly because of the wide repertoire of the S0–S1 energy gaps and electronic densities experienced in solution by the different conformers actually populated. In particular,
all the investigated OT display a very high flexibility resulting in a very high repertoire of sampled conformations. The
comparison of the calculated and experimental lineshape of the S0–S1 electronic transition has clearly indicated that for a correct modeling of OT spectral features, the lack of an exhaustive
sampling of semiclassical configurational space of the overall system, i.e., solute in interaction with the solvent, might
result in an incomplete picture even in the presence of well-documented important aspects such as reliable definition of excited
electronic states and the inclusion of quantum vibronic effects. 相似文献
13.
N. Zh. Saifullina E. B. Galieva A. K. Tashmukhamedova 《Chemistry of Heterocyclic Compounds》2005,41(9):1183-1185
A method has been developed for the introduction of benzimidazole substituents into the dibenzo-18-crown-6 molecule by condensation
of its 4′,4″(5″)-diacetyl derivative with ortho-phenylenediamine. Increasing the length of the hydrocarbon chain of the acyl
substituent or replacing Ac by CSNH2 led to a decrease in the yield of the desired product. No product was formed when Ac was replaced by COOH or CN.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, 1388–1390, September, 2005. 相似文献
14.
Seon-Mi Seo Hak-Ju Lee Oh-Kyu Lee Hyun-Jin Jo Ha-Young Kang Don-Ha Choi Ki-Hyon Paik M. Khan 《Chemistry of Natural Compounds》2008,44(4):419-423
A new furofuran lignan (1) along with four knownones (2-5) were isolated from the bark of Magnolia kobus. Their structures were elucidated as (+)-2α-(3’,4’-dimethoxyphenyl)-6α-(3″-hydroxy-4″,5″-dimethoxyphenyl)-3,7-dioxabicyclo[3.3.0]octane
(1), (+)-sesamin (2), (+)-yangambin (3), (+)-kobusin (4), and (+)-eudesmin (5) on the basis of their comprehensive spectroscopic analysis, including 2D NMR, and by comparison of their spectral data with
those of related compounds.
Published in Khimiya Prirodnykh Soedinenii, No. 4, pp. 338–341, July–August, 2008. 相似文献
15.
The usefulness of ion mobility spectrometry as a screening methodology for the on-site benzodiazepine analysis in saliva samples
has been critically evaluated. The procedure involved the injection of clear supernatant extracts after centrifugation and
provided limit of detection values ranging from 2.0 to 18 μg L−1, and a precision, expressed as relative standard deviation, from 2.9% to 16%, depending on the different benzodiazepines
studied. Those values are appropriate for their positive identification in saliva samples in which benzodiazepine concentration,
after a chronic or acute dose, is in the range of 2–30 μg L−1. Problems related with overlapped benzodiazepine signals have been successfully overcome by application of multivariate curve
resolution, which is a helpful tool to improve the resolution of the technique, without sacrificing the method simplicity
and frequency of analysis. The possibility of false positives caused by the presence of interferents with the same drift time
as the benzodiazepines and the possibility of false negatives due to the presence of interferents by competitive ionization
have been critically evaluated. The satisfactory results obtained for the analysis of real saliva samples after an acute dose
of diazepam through sublingual and oral intakes confirm the capability of the technique to be used as a screening methodology
in the analysis of benzodiazepines in oral fluids. 相似文献
16.
This paper studies the crystal structure of new substituted light-sensitive azomethine N-oxides (nitrones): C-2′-(o-oxyphenyl)vinyl-N-p-methylphenyl
nitrone (1), C-2′-(2″-oxy-5″-bromophenyl)vinyl-N-p-methylphenyl nitrone (2), C-2′-(2″-oxy-5″-bromophenyl)-vinyl-N-phenyl nitrone
(3), and C-2′-(o-oxyphenyl)vinyl-N-methyl nitrone (4). In contrast to the compounds studied earlier [1, 2], C-2′-(β-oxy-α-naphthyl)vinyl-N-p-methylphenyl
nitrone (5), C-2′-(β-oxy-α-naphthyl)vinyl-N-phenyl nitrone (6), C-2′-(o-oxyphenyl) vinyl-N-phenyl nitrone (7), and C-2′-(o-oxyphenyl)vinyl-N-p-bromophenyl
nitrone (8), the nitrones studies in this work have anti-rather than syn-orientations of the nitrone and hydroxyl groups.
Due to this spatial arrangement of the proton-donating hydroxyl and proton-accepting nitrone groups, molecules in crystals
1–4 are bonded by intermolecular hydrogen bonds (IHB) to form chains but not centrosymmetric dimeric associates (CDA). Two
types of chain arrangements were revealed: “head-to-tail” and “head-to-tail, tail-to-head”. It is shown that the introduction
of an alkyl substituent instead of an aryl one at the nitrogen atom of the nitrone group in 4 leads to a change in the geometry
of the IHB in the H-associate. It is proven that the hydroxyl proton can undergo an intermolecular O→O transfer in the chain
of hydrogen bonds in crystals 1–4, which can give rise to photochemical transformations in these crystals.
Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 2, pp. 349–362, March–April, 1996.
Translated by L. Smolina 相似文献
17.
Neng Zhou Yi-Zeng Liang Ben-Mei Chen Ping Wang Xian Chen Feng-Ping Liu 《Chromatographia》2007,66(7-8):481-486
A rapid, simple and specific liquid chromatography-electrospray ionization mass spectrometry method has been developed and
validated for the determination of hydroxyzine hydrochloride in human plasma. Samples were separated using a Thermo Hypersil-HyPURITYC18
reversed-phase column (150 mm × 2.1 mm i.d., 5 μm). The mobile phase consisted of 50 mM ammonium acetate (pH 4.0)–methanol–acetonitrile
(45:36:19, v/v). Hydroxyzine and its internal standard were measured by electrospray ion source in positive selective ion monitoring mode.
The method was validated with a linear range of 1.56–200.0 ng mL−1 and the lowest limit of quantification was 1.56 ng mL−1 for hydroxyzine hydrochloride (r
2= 0.9991). The extraction efficiencies were about 70% and recoveries of the method were in the range of 93.5–104.4%. The intra-day
relative standard deviation (RSD) was less than 8.0% and inter-day RSD was within 7.4%. QC samples were stable when kept at
ambient temperature for 12 h at −20 °C for 30 days and after four freeze–thaw cycles. The method has been successfully applied
to the evaluation of pharmacokinetics and bioequivalence of two hydroxyzine hydrochloride formulations in 12 healthy Chinese
volunteers after an oral dose of 25 mg. 相似文献
18.
The robustness of Shewhart control charts for subgroup means and subgroup ranges was tested by using the Monte Carlo method
using training data sets comprising various numbers of points, with two repetitions in each subgroup (as in routine laboratory
practice). The following control chart designs were tested: conventional based on the arithmetic mean and standard deviation,
robust based on the median and/or the trimmed mean and Winsorized standard deviation, and a two-step design. The methods were
applied to the system in the state of statistical control (outliers excluded) and to the system without statistical control
(outliers included). Satisfactory results for both cases were only obtained when using the two-stage control charts. The conventional
charts led to underestimation of the effect of outliers in the system without statistical control, whereas the robust control
charts led to overestimation of the effect of outliers (false alarm) in the system under statistical control. The tests also
gave evidence that the training set should include 20 points as a minimum.
Received: 13 January 1997 Accepted: 12 February 1997 相似文献
19.
Mourad Ibrahim Daoudi Abdelhafid Triki Abdelkrim Redjaimia 《Journal of Thermal Analysis and Calorimetry》2011,104(2):627-633
Kinetics of β″ and β′ precipitations in an AlSiMg have been studied under non-isothermal conditions using differential scanning
calorimetry (DSC) technique. The variation of the activation energy as a function of transformed fraction is determined using
two isoconversional methods of Kissinger–Akahira–Sunose (KAS) and Friedman. The results obtained using the two methods show
a change in the activation energy for both metastable phases precipitations as a function of transformed fraction. The results
obtained from KAS method as compared with those obtained from Friedman method, show some major disagreements between the two
methods. The growth exponent, determined by Ozawa method, decreases as a function of temperature for both phases. 相似文献
20.
T. V. Tyumkina I. F. Nuriev L. M. Khalilov V. R. Akhmetova U. M. Dzhemilev 《Chemistry of Natural Compounds》2009,45(1):61-65
The structure of a new compound was determined using PMR and 13C NMR spectroscopy (HHCOSY, HSBC, HMBC, ROESY) as 2-[3′-methoxy,4-O-β-D-galactopyranos-1-yl)benzyl]-3-(3″,4″-dimethoxybenzyl)-4hydroxybutyric acid, which was isolated for the first time from
seeds of Scotch thistle Onopordum acanthium L.
*For No. XII, see [1].
Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 53–55, January–February, 2009. 相似文献