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PubMed2006

[Fluorescence spectrum of cesium vapor resonantly excited by the 852.3 nm laser line].

The fluorescence spectrum of cesium vapor was studied in a cell irradiated with the light of 852.3 nm resonance line from a single mode laser diode. From the intensities and spectra of the Cs and Cs2 fluorescence we identified several collisional and radiative processes in the excited cesium atom-dimer system. The atomic lines of the highly excited states were the result of collisional energy transfer from Cs(6P 3/2) + Cs(6P 3/2) to Cs(6D, 8S) atoms. The Cs2 (B 1 IIu) band formed in Cs (6P) + Cs2 (X1sigmag+) collisions. The fine-structure mixing in 6 2P atoms was studied through excitation transfer, energy-pooling collision, and collisional excitation transfer between Cs2 and Cs. The authors estimated the value of rate coefficient for the collisional energy transfer from 6P3/2 to 6P1/2 to be (5.2+/-2.1) x 10(-11) cm3 x s(-1). For the excitation transfer process Cs2 (B 1 IIu)+ Cs(6S)--> Cs2 (X 1sigmag+) + Cs(6P1/2 ), a rate coefficient of (1.0+/-0.4) x 10(-9) cm3 x s(-1) was yielded.

Algorithms↗
PubMed1992

Whole-body cesium 137 activity up to 4 years after the Chernobyl reactor accident in premature newborns, newborns, infants, and children.

Cesium 137 activity was measured after the Chernobyl incident in a whole-body radiation counter (4-pi-scintillation counter) in 85 premature and mature newborns (group 1), 174 infants and young children up to 2 11/12 years (group 2), and 48 children between 3 and 8 years (group 3) from Bonn (Germany) and surroundings. In 1987 the mean level of radioactivity in group 2, at 3.7 Bq/kg body weight corresponding to a mean radiation exposure of 11 muSv/y, was lower than that of group 1 (5.8 Bq/kg, 17 muSv/y) and 3 (9.4 Bq/kg, 28 muSv/y). Up to 1990 the values of all groups revealed a continuous decrease. The latest measurements showed mean values of 0.5 Bq/kg (1.5 muSv/y) in group 1, 0.6 Bq/kg (1.8 muSv/y) in group 2, and 0.8 Bq/kg (2.4 muSv/y) in group 3. A comparison with present cesium 137 values and determinations of the end of the 1950s and beginning of 1960s, both in adults, showed good agreement. The effective dose-equivalent rates amounted to less than 1% of that from natural radiation exposure. These levels should present no teratogenic risks to the population studied and, while there are theoretical mutagenic risks, the dose is so low that no increase in measurable mutagenic effects should be observed.

Accidents↗
PubMed1982

PETT VI: a positron emission tomograph utilizing cesium fluoride scintillation detectors.

We designed and built a positron emission transverse tomograph (PETT VI), designed specifically for fast dynamic studies in the human brain, and for cardiac studies in experimental animals. The scintillation detectors incorporated into this device are fitted with cesium fluoride crystals. Cesium fluoride was selected for this purpose because its short fluorescence decay allows the use of a short coincidence resolving time with a concomitant reduction of unwanted random coincidences. PETT VI utilizes four rings of 72 detectors simultaneously yielding seven tomographic sections. The system can be operated in either a low or high resolution mode with intrinsic geometrical resolutions in the plane of section of 7.1 to 11.7 mm full width at half maximum (FWHM), for a slice thickness with a resolution at the center of 13.9 mm FWHM. The maximum sensitivity of the system for seven slices in the low resolution mode is 322,000 cps/microCi/cc in a 20 cm diameter phantom. The contribution of random coincidences before subtraction in PETT VI was found to be approximately 14% of the counts in the phantom image with a source of approximately 3.5 mCi of a positron emitting radionuclide dispersed in a 20 cm diameter tissue equivalent phantom with a concentration of 1 microCi/cc. The short coincidence resolving time of the system permits rapid data acquisition for attenuation corrections and clinical dynamic studies with data acquisition times of less than a minute.

Animals↗
PubMed1981

[Effect of the diethylamine analog of etmozin and cesium chloride on the idioventricular rhythm in dogs in the late stages of experimental myocardial infarct].

Atrioventricular block was produced by infusion of 0.1-0.2 ml of 40% formaline into the A-V node or the bundle of His. Effect of diethylamine analog of etmozin (1 mg/kg) and cesium chloride (20 mg/kg) on the idioventricular rate was studied in control and experimental dogs 24 hours after the occlusion of the coronary artery. It was shown that cesium ions inhibit the idioventricular rate in the normal canine heart (from 49.9 +/- 3.8 to 6.9 +/- 4.5/min; p less than 0.001, n = 7) and have no influence on the ectopic ventricular rate in the late stage of myocardial infarction. On the contrary, diethylamine analog of etmozin has no significant effect on normal ventricular automatism and considerably reduces the ectopic ventricular rate (from 111.5 +/- 7.2 to 23 +/- 15.6/min; p less than 0.001, n = 8). The evidence points to the difference between the ionic mechanisms determining the normal specialized conduction system automatism and the ionic mechanisms which are responsible for the enhanced automatism in the late stage of experimental myocardial infarction.

Animals↗
PubMed1976

[Blastomogenic effect following single and chronic exposure to a mixture of cesium-137 and strontium-90].

The rate of tumor incidence in different rhythms of rat stomach exposure to cesium-137 and strontium-90 was analysed. The correlative values of the administered nucleids activity were selected by analogy with their content in global natural fall-out. In single exposure to the concentrations of 400 and 100 mc/per rat of cesium-137 and strontium-90 mixture accordingly, osteogenic osteosarcomas developed approximatley 4 times as frequently as in chronic administration of the same radionucleids in concentrations of 2 and 8 mc/per rat, correspondingly.

Adenoma↗
PubMed1994

[Measuring cesium 137 concentrations in surgical specimen of gynecologic tumors and breast milk, amniotic fluid and in umbilical cords, 6 years after Chernobyl].

In the present study, the cesium 137 content in various human tissues was examined 6 years after the Chernobyl reactor catastrophe. The measurements were performed with a gamma-ray spectrometer by means of a germanium/lithium detector. The median of cesium 137 was 20 mBq/ml in mother's milk, 60 mBq/ml in amniotic fluid, 105 mBq/g in umbilical cords, 51 mBq/g in ovarian tumours, and 140 mBq/g in mammary carcinomas. These values lay far below the permissible limit values of 528 mBq/ml or 528 mBq/g for persons not exposed to radiation. The problems of determining the upper limit were also discussed, and it was ascertained that despite the favorably low values recorded in this study a residual risk to health cannot be absolutely precluded in the light of present-day knowledge.

Amniotic Fluid↗
PubMed1977

[Evaluation of the protective effect of Prussian blue, sodium alginate and calcium phosphate according to tumor development after single and chronic exposure to strontium 90 and cesium 137 mixture].

The mixture of radionuclides was employed in the concentrations of 100.0, 400.0 and 0.8, 2.0 mc/rat for strontium-90 and cesium-137 in single and chronic administration correspondingly. Prussian blue, sodium alginate and calcium were employed in amounts of 50 mg, 800 mg and 258 mg per rat a day. The data obtained are correlated with the results of the same experiments without using the protection. In compared doses of the irradiation the protective action of the substances under study was noted only in chronic experiments. In this case, the appearance of malignant neoplasms was nearly twice less, and the survival was 120 days longer. The absorbed doses were decreased by 17 times for cesium-137 in the whole body and nearly by 4 times for strontium-90 in the skeleton.

Alginates↗
PubMed1996

Determination of cesium, manganese and terbium by intracavity laser spectroscopy.

The statistical characteristics of the intracavity laser spectrometer are investigated by analysis of cesium in aqueous solutions. The error distribution of measurements is normal. The relative standard deviation of the analysis in the middle of the dynamic range is equal to 9.7%. The intracavity spectral analysis was carried out at low contents of cesium, manganese and terbium in aqueous solutions. The limits of detection are: 5 microg l(-1) (Cs), 20 microg l(-1) (Mn) and 1000 microg l(-1) (Tb). Owing to the high spectral resolution of the spectrometer used the hyperfine structure of the thallium absorption line (535.05 nm) was recorded.

Journal Article↗
PubMed2006

The uncertainties associated with the application of batch technique for distribution coefficients determination--a case study of cesium adsorption on four different bentonites.

The uncertainties associated with the batch method used often as adsorption data source for performance assessments of radioactive waste repositories have been analyzed and evaluated. The adsorption of cesium on four different bentonites (two Na- and two Ca-bentonites) using a radiotracer ((137)Cs) technique has been studied to evaluate experimental uncertainties and compare their effects on calculated distribution coefficients (K(d)s). Three main factors influencing uncertainty of K(d) at given conditions were identified-the radiotracer operation (mainly tracer addition to experimental systems), the phase separations efficiency and the mineralogical heterogeneity of samples. It was found that the determination of quantitative contributions of the last two factors to the uncertainty of K(d) is difficult, depending on input material and conditions. The centrifugation and ultrafiltration method has been tested for removing colloids in sample solutions, but the results obtained were disputable. The mineral heterogeneity (complex mineral composition) effect has been identified mainly in kinetics of cesium adsorption where three different trends were described. This has important influence on the time-scale of the experiment's planning and equilibrium time estimation or identification. It has been concluded that experimental procedure may represent important uncertainty source of calculated K(d). In performance assessment studies, this uncertainty of K(d) given by the appropriate experimental procedure should be taken into account and properly evaluated.

Journal Article↗
PubMed2003

Isolation of DNA-free RNA, DNA, and proteins by cesium trifluoroacetate centrifugation.

The ability to simultaneously isolate intact DNA-free RNA, genomic DNA, and proteins from a biological specimen can be useful in cloning genes and analyzing gene expression. Equilibrium density gradient centrifugation with CsCl is a useful tool for fractionating, quantitatively separating, and characterizing RNA, DNA, and the total quota of proteins, respectively, based on differences in their buoyant densities. In the present study we have reexamined the rarely used cesium salt, cesium trifluoroacetate, for the same purpose. A significant advantage of CsTFA lies in the fact that, unlike in CsCl, RNA can be recovered from a single, soluble fraction of the CsTFA gradient. Furthermore, unlike CsCl, CsTFA is freely soluble in ethanol so that co-precipitation of the salt in the recovered RNA upon alcohol precipitation does not take place. Hence, the RNA is recovered with minimum manipulations. The one-step separation of cellular macromolecule classes free of each other in small amount of starting materials provides a major advantage over other methods currently in use.

Cell Line↗
PubMed2004

Extraction of cesium ions from aqueous solutions using calix[4]arene-bis(tert-octylbenzo-crown-6) in ionic liquids.

Solvent extraction of cesium ions from aqueous solution to hydrophobic ionic liquids without the introduction of an organophilic anion in the aqueous phase was demonstrated using calix[4]arene-bis(tert-octylbenzo-crown-6) (BOBCalixC6) as an extractant. The selectivity of this extraction process toward cesium ions and the use of a sacrificial cation exchanger (NaBPh(4)) to control loss of imidazolium cation to the aqueous solutions by ion exchange have been investigated.

Journal Article↗
PubMed2003

Aggregation and reactivity of the cesium enolate of 6-phenyl-alpha-tetralone: comparison with the lithium enolate.

The cesium enolate of 6-phenyl-alpha-tetralone (CsPAT) has a lambda(max) in THF at about 387 nm, but the variation with concentration is too small for application of singular value decomposition. Proton-transfer studies with several indicators show that CsPAT forms monomer-tetramer mixtures with a tetramerization equilibrium constant, K(1,4) = 2.3 x 10(11) M(-3). The pK of the monomer is 23.39 on a scale where fluorene is assigned 22.9 (per hydrogen). For comparison, the lithium enolate, LiPAT, is also a monomer-tetramer with K(1,4) = 4.7 x 10(10) M(-3) and a monomer pK = 14.22. HMPA in large amounts promotes dissociation to monomer with both enolates. Ion-pair S(N)2 initial rates were measured for CsPAT with several alkyl halides and with methyl tosylate and compared with other rates with LiPAT. In all cases, the enolate monomers are much more reactive than the aggregates. Reaction of CsPAT with alkyl halides is generally C-alkylation but HMPA promotes increasing amounts of O-alkylation. A new indicator, 11-methyl-11H-benzo[b]fluorene, has a pK on the cesium scale of 23.39.

Journal Article↗
PubMed1996

Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran(1).

The equilibrium lithium acidities in THF have been determined for 4-ethynylbiphenyl, EB (pK 21.5-22.3), 3,3,3-triphenylpropyne, TPP (pK 22.3-22.7), and 1-ethynyladamantane, EA (pK 23.7). Ion pairs of (4-ethynylbiphenylyl)lithium are aggregated in the concentration range from 10(-)(4) to 10(-)(3) M, with an average aggregation number of 2.5. (3,3,3-Triphenylpropynyl)lithium ion pairs are partially aggregated at concentrations from 10(-)(5) to 10(-)(3) M; the average aggregation number is 1.2. Cesium acidities in THF have been determined for 3,3,3-triphenylpropyne (pK 29.1-29.9) and 1-ethynyladamantane (pK 31.56). The average aggregation number of (3,3,3-triphenylpropynyl)cesium ion pairs is 6.2 at concentrations of 10(-)(4)-10(-)(3) M.

Journal Article↗
PubMed1999

Cesium Fluoride Catalyzed Trifluoromethylation of Esters, Aldehydes, and Ketones with (Trifluoromethyl)trimethylsilane.

The low reactivity of carboxylic esters toward (trifluoromethyl)trimethylsilane (TMS-CF(3)) was investigated. A universal cesium fluoride catalyzed procedure for nucleophilic trifluoromethylation was developed. At room temperature (25 degrees C), with catalytic amounts of cesium fluoride, carboxylic esters were found to react to give the silyl ether intermediates, which afforded the trifluoromethyl ketones after hydrolysis. Sulfonic, sulfinic, and selenic esters also show good reactivity, giving novel trifluoromethylated compounds. The trifluoromethylation method was also applied to aldehydes and ketones, which were transformed to trifluoromethyl silyl ether intermediates and afforded trifluoromethylated alcohols in excellent yields after acid hydrolysis. Ethylene glycol dimethyl ether was used as solvent for solid or high boiling substrates, and benzonitrile was used for the low boiling substrates.

Journal Article↗
PubMed2006

Cesium dimer spectroscopy on helium droplets.

Visible absorption spectra of cesium-doped helium nanodroplets between 14,500 and 17,600 cm(-1) were probed by laser-induced fluorescence. A strong absorption band peaking around 16,700 cm(-1) is identified as Cs2 1(a) 3Sigmau+-3 3Sigmag+ transition. A broad unstructured band near 17,520 cm(-1) is assigned as the Cs2 1(X) 1Sigmag+-2 1Sigmau+ transition. Explanations of the observations are discussed on the basis of ab initio potential curves calculated by Spies and Meyer [(unpublished)]. All spectra have been modeled using narrow Frank-Condon windows around the equilibrium internuclear distance of the lowest singlet and triplet states. Many observed absorption peaks of smaller intensities could be identified, some of which may be due to transitions of cesium trimers formed on the droplets.

Journal Article↗
PubMed2006

Geometrical and electronic properties of neutral and charged cesium clusters Cs(n) (n=2-10): a theoretical study.

We have investigated the structure and electronic properties of cesium clusters following all electron ab initio theoretical methods based on configuration interaction, second-order Moller-Plesset (MP2) perturbation theory, and density-functional theory. Becke's three-parameter nonlocal hybrid exchange-correlation functional (B3LYP) is found to perform best on the present systems with a split valence 3-21G basis function. We have calculated the optimized geometries of neutral and singly charged cesium clusters having up to ten atoms, their binding energy per atom, ionization potentials (IPs), and adiabatic electron affinity (EA). Geometry optimizations for all the clusters are carried out without imposing any symmetry restriction. The neutral clusters having up to six atoms prefer planar structure and three-dimensional structure is preferred only when the number of atoms in a cluster is more than six. There is a good agreement between the present theoretical and reported experimental IP values for the neutral clusters with cluster size n<or=10. Calculated EA is also in good agreement with the available experimental data for the small Cs clusters. Similar calculations have also been carried out for small Rb clusters and the performance of B3LYP is equally good. Thermodynamic properties such as enthalpy and entropy for small Cs and Rb clusters have also been calculated and are well compared with the experimental data.

Journal Article↗
PubMed2001

Time-scale invariance of relaxation processes of density fluctuation in slow neutron scattering in liquid cesium.

The realization of the idea of time-scale invariance for relaxation processes in liquids has been performed by the memory functions formalism. The best agreement with experimental data for the dynamic structure factor S(k,omega) of liquid cesium near melting point in the range of wave vectors (0.4 A(-1) < or = k < or = 2.55 A(-1)) is found with the assumption of concurrence of relaxation scales for memory functions of third and fourth orders. Spatial dispersion of the first four points in the spectrum of the statistical parameter of non-Markovity epsilon(i)(k,omega) at i=1,2,3,4 has allowed us to reveal the non-Markov nature of collective excitations in liquid cesium, connected with long-range memory effect.

Journal Article↗