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At least 235 records · Page 13Linked to original sources
PubMed2005

Using Cesium-137 technique to study the characteristics of different aspect of soil erosion in the Wind-water Erosion Crisscross Region on Loess Plateau of China.

The most serious soil erosion on Loess Plateau exists in the Wind-water Erosion Crisscross Region. In the past 20 years, the types and intensity of soil erosion and its temporal and spatial distribution were studied, but studies on the difference of soil erosion between slope aspects and slope positions in this area have no report. However, it is very important to analyze and evaluate quantitatively the characteristics of different aspects and positions of soil loss for the prevention and treatment of soil erosion in this area. The spatial pattern of net soil loss on 4 downslope transects in four aspects (east, west, south and north) on a typical Mao (round loess mound) in Liudaogou catchment in Wind-water Erosion Crisscross Region was measured in 2000 using the resident cesium-137 deficit technique. The purposes of this investigation were undertaken to determine whether or not 137Cs measurement would give a useful indication of the extent of soil loss and their characteristics from cultivated hillsides in different slope aspect and slope position in the study area. The results showed that the difference of soil erosion in different aspect was significant and the erosion rate was in this order: north > east > south > west. Compared with other areas, the difference of erosion rate between north hillside and south hillside was on the contrary, and the possible explanations could be the effect of wind erosion. Also, the percentage of wind erosion was estimated to be at least larger than 18% of total soil loss by comparing the difference of erosion amount in south hillside and north hillside. The erosion rates on different slope positions in all aspects were also different, the highest net soil loss occurred in the lower slope position, and the upper and middle slope positions were slight. The general trend of net soil loss on sloping surface was to increase in fluctuation with increasing downslope distance.

Cesium Radioisotopes↗
PubMed2006

Acidic cesium salts of 12-tungstophosphoric acid as catalysts for the dehydration of xylose into furfural.

Cesium salts of 12-tungstophosphoric acid, Cs(x)H(3-x)PW(12)O(40) (Cs(x)PW), in the bulk form or supported on medium-pore MCM-41 (3.7 nm) or large-pore (9.6 nm) micelle-templated silicas are active solid acid catalysts for the cyclodehydration of xylose into furfural, in a toluene/water solvent system (T/W) or in dimethyl sulfoxide (DMSO). The catalytic results are comparable to those obtained using sulfuric acid, under similar reaction conditions. The initial activities increase in the order H(3)PW(12)O(40)<Cs(2.0)PW<Cs(2.5)PW<silica-supported CsPW catalysts (15, 34wt% PW). Higher HPA loadings, larger pore diameter of the parent silica support, and higher reaction temperatures lead to higher furfural yields. The stability and reusability of the MCM-41-supported CsPW is higher in DMSO than in T/W.

Catalysis↗
PubMed2005

Cesium-137 in grass from Chernobyl fallout.

Grass ecosystem was monitored for 137Cs, a relatively long-lived radionuclide, for about 16 years since the Chernobyl reactor accident occurred on April 26, 1986. Cesium-137 in grass gramineae or poaceae the species, ranged from 122.9 Bq kg(-1) (September 4, 1986) to 5.8 mBq kg(-1) (October 16, 2001) that is a range of five orders of magnitude. It was observed that there was a trend of decreasing 137Cs with time reflecting a removal half-time of 40 months (3 1/3 years), which is the ecological half-life, T(ec) of 137Cs in grassland.

Animals↗
PubMed2005

Weather-dependent change of cesium, strontium, barium and tellurium contamination deposited as aerosols on various cultures.

Various types of plants (wheat, bean, lettuce, radish and grass) were contaminated by dry deposition of radioactive aerosols ((137)Cs, (85)Sr, (133)Ba and (123 m)Te) in order to supplement the radio-ecological data necessary for operational post-accidental codes. A few days after deposition, rainfalls were applied to these cultures to evaluate the influence of some characteristics of the rain on the contamination of the culture over time. On the other hand, for wheat and bean, the influence of the humidity condition of the foliage at the contamination time was considered. For a given plant species at a given vegetative stage, the four radionuclides were intercepted in an identical way. The interception varied from 30% for bean (young sprout) to 80% for lettuce (near maturity). The global transfer factor values were dependent on both the radionuclides and the plant species; nevertheless, a higher value was obtained for cesium, regardless of the plant and the rainfall (from 0.006 m(2)kg(fresh)(-1) for wheat-grains - contaminated at the shooting stage - or for bean-pods - contaminated at the pre-flowering stage - to 0.1m(2)kg(fresh)(-1) for a whole lettuce). The analysis of the results allowed us on the one hand, to extract parameter values of the foliar transfer directly usable in operational codes, in particular those relating to barium and tellurium, unknown until then, and on the other hand, to lay the foundations of a future, more mechanistic model, taking into account the foliar processes in a finer way.

Aerosols↗
PubMed2005

Foliar uptake of cesium from the water column by aquatic macrophytes.

The probable occurrence and rate of foliar absorption of stable cesium (133Cs) from the water column by aquatic macrophyte species was analyzed following the addition of 133Cs into a small reservoir near Aiken, South Carolina, USA. An uptake parameter u (10(3)Lkg(-1)d(-1)) and a loss rate parameter k (d(-1)) were estimated for each species using time series of 133Cs concentrations in the water and plant tissues. Foliar uptake, as indicated by rapid increases in plant concentrations following the 133Cs addition, occurred in two floating-leaf species, Brasenia schreberi and Nymphaea odorata, and two submerged species, Myriophyllum spicatum and Utricularia inflata. These species had values of u> or =0.75 x 10(3)Lkg(-1)d(-1). Less evidence for foliar uptake was observed in three emergent species, including Typha latifolia. Ratios of u to k for B. schreberi, M. spicatum, N. odorata and U. inflata can be used to estimate concentration ratios (CR) at equilibrium, and these estimates were generally within a factor of 2 of the CR for 137Cs for these species in the same reservoir. This correspondence suggests that foliar uptake of Cs was the principal absorption mechanism for these species. Assessments of: (1) the prevalence of foliar uptake of potassium, rubidium and Cs isotopes by aquatic macrophytes and (2) the possible importance of foliar uptake of Cs in other lentic systems are made from a review of foliar uptake studies and estimation of comparable u and k values from lake studies involving Cs releases.

Cesium Radioisotopes↗
PubMed2005

Non-isothermal kinetics of the dehydration reaction of 3-nitro-1,2,4-triazol-5-one rubidium and cesium complexes.

3-Nitro-1,2,4-triazol-5-one (NTO) rubidium and cesium complexes were synthesized by mixing the aqueous solution of NTO and their respective metal carbonates. Their thermal decomposition and the non-isothermal kinetics of the dehydration reaction were studied under the non-isothermal condition by DSC and TG-DTG methods. The kinetic parameters were obtained from analysis of the DSC and TG-DTG curves by Kissinger method, Ozawa method, the differential method and the integral method. The most probable mechanism functions for the dehydration reaction of the title complexes were suggested by comparing the kinetic parameters. The dehydration decomposition reaction of RbNTO.H2O and CsNTO.H2O appears to be the same as Avrami-Erofeev equation: f(alpha) = (5/2)(1-alpha)[-ln(1-alpha)](3/5), G(alpha)=[-ln(1-alpha)](2/5), n = 2/5. The critical temperature of thermal explosion is 240.88 degrees C for RbNTO.H2O and 246.27 degrees C for CsNTO.H2O.

Cesium↗
PubMed2004

Purification of Toxoplasma gondii oocysts by cesium chloride gradient.

We describe the use of a cesium chloride (CsCl) gradient as an improvement for the purification of Toxoplasma gondii oocysts from concentrated suspensions. After concentration by sucrose flotation, this technique gives a > 96% recovery of very pure unsporulated or sporulated oocysts, but requires "fresh" oocysts (< or = 10 weeks of age). This material is suitable for biochemical and immunological analyses of environmentally resistant T. gondii oocysts.

Animals↗
PubMed1986

Internal cesium and the sodium inactivation gate in Myxicola giant axons.

Internal cesium (CSi), relative to internal potassium (Ki), alters Na current (INa) time course in internally perfused Myxicola giant axons. CSi slows the time to peak INa, slows its decline from peak and increases the steady state to peak current ratio, INainfinity/INapeak. Neither activation nor deactivation kinetics are appreciably affected by CSi. Na current rising phases, times to half maximum and tail current time courses are similar in CSi and Ki. Inactivation time constants determined by both one (tau h) and two (tau c) pulses are also little changed by CSi. The CSi effects are due largely or entirely to an increased INainfinity/INapeak. CSi decreases the steady level of inactivation reached during a step in potential, preventing some fraction of inactivation gates from closing at all, the rest apparently closing normally. Inactivation block in CSi decreases with increasing inward current magnitude and in Ki inactivation block is appreciable only for outward Na channel current, suggesting the site of action is located somewhere in the current pathway. If this site mediates the normal operation of the inactivation gate, then a possible mechanism for gate closure could involve a positively charged structure moving to associate with a negative site near or into the inner channel mouth.

Animals↗
PubMed2003

Effect of the nature of the counterion on the interaction between cesium and tetraalkylammonium dodecylsulfates and poly(ethylene oxide) or poly(vinylpyrolidone).

The interaction between poly(ethylene oxide) or poly(vinylpyrrolidone) and cesium and tetraalkylammonium (tetramethyl to tetrabutyl ammonium) dodecylsulfate has been investigated by means of electrical conductivity measurements to determine the critical aggregation concentration (cac) of the surfactants in the presence of polymer. The cac values were compared to the values of the critical micellization concentration (cmc) of the surfactants in the absence of polymer. The value of the cac/cmc ratio increased with the radius of the counterion in the sequence: Na(+)<Cs(+)<tetramethylammonium(+)<tetraethylammonium(+)=tetrapropylammonium(+)=tetrabutylammonium(+)=1.0. This result indicates that the strength of the interaction decreases upon increasing counterion radius. For the last three tetraalkylammonium ions the value cac/cmc=1 indicates the absence of interaction. The results are discussed in an attempt to gain a better understanding of the mechanism of formation of surfactant aggregates bound to water-soluble polymers such as poly(ethylene oxide) or poly(vinylpyrrolidone).

Alkanesulfonic Acids↗
PubMed1995

Cesium effects on dual pacemaker mechanisms in guinea pig sinoatrial node.

The aim of the present experiments was to study the effects of cesium (Cs) on dual pacemaker potentials and the underlying mechanisms in isolated sinoatrial (SA) node of the guinea pig superfused in vitro. Cs (1-20 mM) initially hyperpolarized the maximum diastolic potential (MDP) and then depolarized it in a concentration-dependent manner. In subsidiary pacemaker cells of the SA node, increasing [Cs]o abolished diastolic depolarization (DD), but then (by depolarizing the cells to less negative potentials) Cs allowed the appearance of a shallow DD that maintained spontaneous discharge even in 20 mM Cs. In 10 mM [K]o, the subsidiary pacemaker cells depolarized and exhibited action potentials similar to those in dominant pacemaker cells. In high [K]o, the Na/K pump activity is stimulated: adding Cs initially increased the MDP minimally, but the subsequent decrease in MDP persisted. In preparations quiescent in high [K]o, Cs only depolarized the membrane and could induce spontaneous discharge: the action potentials were followed by an undershoot and DD. In high [K]o plus norepinephrine, even 20 mM Cs did not suppress and might increase the rate of discharge. During quiescence in acetylcholine or carbachol (I(f) is blocked), Cs still transiently hyperpolarized the resting potential. In zero [K]o with or without carbachol (I(f) is absent or blocked), Cs hyperpolarized the quiescent membrane by stimulating the Na/K pump. Cs-induced hyperpolarization was reduced by 50-100 microM ouabain. We conclude that, in the SA node, dual pacemaker mechanisms are present in subsidiary cells. The pacemaker potential at more negative voltages is blocked by Cs, but the dominant type pacemaker potential is not blocked even by 20 mM Cs (which is known to completely block I(f). Cs initially hyperpolarizes apparently by stimulating the Na/K pump (not by blocking I(f)) and subsequently depolarizes the subsidiary pacemaker cells by blocking an outward current but not IK1 (absent in the SA node). Thus, in the SA node I(f) may play little role in pacemaker activity.

Acetylcholine↗
PubMed2003

A physiologically based biokinetic model for cesium in the human body.

A physiologically descriptive model of the biological behavior of cesium in the human body has been constructed around a detailed blood flow model. The rate of transfer from plasma into a tissue is determined by the blood perfusion rate and the tissue-specific extraction fraction of Cs during passage from arterial to venous plasma. Information on tissue-specific extraction of Cs is supplemented with information on the Cs analogues, K and Rb, and known patterns of discrimination between these metals by tissues. The rate of return from a tissue to plasma is estimated from the relative contents of Cs in plasma and the tissue at equilibrium as estimated from environmental studies. Transfers of Cs other than exchange between plasma and tissues (e.g. secretions into the gastrointestinal tract) are based on a combination of physiological considerations and empirical data on Cs or related elements. Model predictions are consistent with the sizable database on the time-dependent distribution and retention of radiocesium in the human body.

Cesium↗
PubMed1998

Accumulation of 210Pb, 226Ra and radioactive cesium by fungi.

Fungi sampled in three areas in France were analyzed by gamma-spectrometry for their concentrations of 134Cs, 137Cs, 210Pb and 226Ra. In most of the samples radioactive cesium was detected with a maximum of 2860 Bq kg-1 (dry wt.). Activity concentrations of 210Pb were in the range < 1.76-36.5 Bq kg-1 (dry wt.). Activity concentrations of 226Ra were consistently lower, often by one order of magnitude. Models are developed to estimate the contributions of atmospheric 210Pb deposited onto the fruit bodies to the measured 210Pb concentrations and of the uptake of 222Rn soluted in soil pore water which subsequently decays into 210Pb. It is shown that both pathways are of only minor importance. Comparison with the soil-mushroom concentration ratios of stable lead, which were determined for some of the samples, confirmed that 210Pb in mushrooms mainly originates from direct uptake of 210Pb present in the soil. Despite of the high concentrations of 137Cs detected in most of the mushrooms, radiation doses to individuals due to mushroom consumption are dominated by 210Pb for the majority of the edible mushrooms sampled.

Agaricales↗
PubMed2003

Cesium-137 concentrations in marine macroalgae from different biotopes in the Aegean Sea (Greece).

The commonest species of red, brown, and green macroalgae were sampled from a range of biotopes in the Aegean Sea during 1998 for their 137Cs content. Significant differences in 137Cs concentrations were found among different species growing under similar environmental conditions, suggesting that uptake does not follow physical levels but is influenced by allometric parameters and physiological mechanisms. 137Cs content in collected seaweeds were in the descending order: Ulva lactuca>Enteromorpha linza>Gracilaria verrucosa>Ceramium rubrum>Cystoseira barbata. A comparison of the stations studied indicated that the degree of accumulation is also dependent on the geomorphology of the specific area. The west side of Thermaikos Gulf, where the rivers Axios, Aliakmon, and Pinios flow, was highly contaminated as was the Strymonicos Gulf where the river Strymon flows. High cesium concentrations were also observed in algae from Lemnos Island near the mouth of the Dardanelles Channel, most likely due to the horizontal circulation of water masses from the Marmaras Sea to the Aegean Sea resulting in the discharge of 137Cs during the purification process in the Black Sea through the Dardanelles Straits. It is concluded that the general dispersion of 137Cs results from the water circulation regime within the Aegean Sea. Higher levels are present in the northern part of the basin due to current circulation originating from the Black Sea and from outflow of rivers. Levels decrease to the south and east, but increase again to the west of Crete where the Black Sea water mass can be periodically traced.

Cesium Radioisotopes↗
PubMed2003

A sensibility analysis of model selection in modeling the reactive transport of cesium in crushed granite.

We performed a sensibility analysis of model selection in modeling the reactive transport of cesium in crushed granite through model calibration and validation. Based on some solid phase analysis data and kinetic batch experimental results, we hypothesized three two-site sorption models in the LEHGC reactive transport model to fit the breakthrough curves (BTCs) from the corresponding column experiments. The analysis of breakthrough curves shows that both the empirical two-site kinetic linear sorption model and the semi-mechanistic/semi-empirical two-site kinetic surface complexation model, regardless of their complexity, can match our experimental data fairly well under given test conditions. A numerical experiment to further compare the two models shows that they behave differently when the pore velocity is not of the same order of magnitude as our test velocities. This result indicates that further investigations to help determine a better model are needed. We suggest that a multistage column experiment, which tests over the whole range of practical flow velocities, should be conducted to help alleviate inadequate hypothesized models.

Calibration↗
PubMed2002

The extracellular current blocking effect of cesium chloride on the theta wave in the rabbit hippocampal CA1 region.

We studied the extracellular effects of cesium chloride (CsCl), a blocker of the hyperpolarization-activated cationic current (I(h)), on the hippocampal theta wave in pentobarbital-anesthetized rabbits. We recorded spontaneous field potentials at the hippocampal CA1 region before and at three time periods after CsCl or saline injections. We found that CsCl injected into the apical dendritic layer attenuated the theta wave amplitude. CsCl affected neither the frequency nor the phase reversal of the theta wave between the apical and basal dendritic layers. Our findings indicate that I(h) in pyramidal neurons contributes to current generation of the limbic theta wave in vivo.

Animals↗
PubMed1998

Photodynamic action of uroporphyrin and protochlorophyllide in greening barley leaves treated with cesium chloride.

Incubation of greening barley leaves with cesium chloride (CsCl) results in photodynamic leaf lesions within 24 h due to an inactivation of uroporphyrinogen III decarboxylase, an enzyme of tetrapyrrole biosynthesis, and transient accumulation of uroporphyrin (ogen). To examine the mechanism of porphyrinogenesis, time kinetics of the accumulating tetrapyrrole intermediates uroporphyrin (ogen) and protochlorophyllide were performed with leaves which were cut from 7-day-old dark-grown barley seedlings and incubated in 15 mM CsCl or water under different light regimes. In the presence of CsCl chlorophyll and carotenoids accumulation was inhibited in the first 24 h of continuous light and the pigment content decreased dramatically during extended illumination. When CsCl=treated leaves were transferred to darkness, accumulated uroporphyrinogen was completely converted to protochlorophyllide. Low temperature fluorescence spectroscopy confirmed that uroporphyrinogen almost completely accumulated in the reduced form. The oxidised form, uroporphyrin, was detectable after 24 h of illumination. The photodynamic leaf lesions became visible at the same time. Protochlorophyllide synthesised from accumulated uroporphyrinogen III in dark incubated leaves had a fluorescence maximum at 635 nm which is indicative for its non-photoconvertible form. Re-illumination of the barley leaves resulted in a rapid degradation of proteins and pigments and an intense lipid peroxidation within less than two hours due to the photodestructive potential of non-metabolised protochlorophyllide.

Carotenoids↗
PubMed2003

FT-IR and Raman spectroscopic analysis of hydrated cesium borates and their saturated aqueous solution.

Hydrated cesium borates have been synthesized by the reaction of Cs(2)CO(3) with H(3)BO(3) aqueous solution. After reaction equilibria were reached, liquid and solid phases were separated and the FT-IR difference and Raman spectra of each phase were recorded, respectively. The assignments of the recorded FT-IR absorption frequencies and Raman shift are given. The main polyborate anions and their interaction in borate aqueous solution have been proposed. The relations between the existing forms of polyborate anions and the crystallizing solid phases, Cs(2)B(4)O(7).5H(2)O and CsB(5)O(8).4H(2)O, have been gained.

Borates↗
PubMed2001

Cesium and strontium ion exchange on the framework titanium silicate M2Ti2O3SiO4.nH2O (M = H, Na).

The ion exchange properties of the titanium silicate, M2Ti2O3SiO4.nH2O (M = H, Na), toward stable and radioactive 137Cs+ and 89Sr2+, have been examined. By studying the cesium and strontium uptake in the presence of NaNO3, CaCl2, NaOH, and HNO3 (in the range of 0.01-6 M) the sodium titanium silicate was found to be an efficient Cs+ ion exchanger in acid, neutral, and alkaline media and an efficient Sr2+ ion exchanger in neutral and alkaline media, which makes it promising for treatment of contaminated environmental media and biological systems.

Cesium↗