Mass conservative three-dimensional water tracer distribution from Markov chain Monte Carlo inversion of time-lapse ground-penetrating radar data

Time-lapse geophysical measurements are widely used to monitor the movement of water and solutes through the subsurface. Yet commonly used deterministic least squares inversions typically suffer from relatively poor mass recovery, spread overestimation, and limited ability to appropriately estimate nonlinear model uncertainty. We describe herein a novel inversion methodology designed to reconstruct the three-dimensional distribution of a tracer anomaly from geophysical data and provide consistent uncertainty estimates using Markov chain Monte Carlo simulation. Posterior sampling is made tractable by using a lower-dimensional model space related both to the Legendre moments of the plume and to predefined morphological constraints. Benchmark results using cross-hole ground-penetrating radar travel times measurements during two synthetic water tracer application experiments involving increasingly complex plume geometries show that the proposed method not only conserves mass but also provides better estimates of plume morphology and posterior model uncertainty than deterministic inversion results.

Measurement of absolute cell volume, osmotic membrane water permeability, and refractive index of transmembrane water and solute flux by digital holographic microscopy.

ABSTRACT. A dual-wavelength digital holographic microscope to measure absolute volume of living cells is proposed. The optical setup allows us to reconstruct two quantitative phase contrast images at two different wavelengths from a single hologram acquisition. When adding the absorbing dye fast green FCF as a dispersive agent to the extracellular medium, cellular thickness can be univocally determined in the full field of view. In addition to the absolute cell volume, the method can be applied to derive important biophysical parameters of living cells including osmotic membrane water permeability coefficient and the integral intracellular refractive index (RI). Further, the RI of transmembrane flux can be determined giving an indication about the nature of transported solutes. The proposed method is applied to cultured human embryonic kidney cells, Chinese hamster ovary cells, human red blood cells, mouse cortical astrocytes, and neurons.

Transport of a biocontrol Pseudomonas fluorescens through 2.5-m deep outdoor lysimeters and survival in the effluent water

Application of wild-type or genetically-modified bacteria to the soil environment entails the risk of dissemination of these organisms to the groundwater. To measure vertical transport of bacteria under natural climatic conditions, Pseudomonas fluorescens strain CHA0 was released together with bromide as a mobile tracer at the surface of large outdoor lysimeters. Two experiments, one starting in autumn 1993 and the other in spring 1994 were performed. Shortly after a heavy rainfall in late spring 1994, the released bacteria were detected for the first time in effluent water from the 2.5-m-deep lysimeters in both experiments, i.e. 210 d and 21 d, respectively, after inoculation. Only a 10−9 to 10−8 fraction of the inoculum was recovered as culturable cells in the effluent water, but a larger fraction of the CHA0 cells was in a non-culturable state as detected with immunofluorescence microscopy. As much as 50% of the mobile tracer percolated through the lysimeters, indicating that, compared with bromide, bacterial cells were retained in soil. In the second part of this study, persistence of CHA0 in groundwater microcosms consisting of lysimeter effluent water was studied for 380 d. Survival of the inoculant as culturable cells was better under anaerobic than under aerobic conditions. However, a large fraction of the cells became non-culturable in both cases. When the experiment was performed with filter-sterilized effluent water, the total count of introduced bacteria did not decline with time. In conclusion, the biocontrol strain was transported in low numbers to a potential groundwater level under natural climatic conditions, but could persist for an extended period in groundwater microcosms.

Effect of bicarbonate and lactate buffer on glucose and lactate metabolism during hemodiafiltration in patients with multiple organ failure.

OBJECTIVE: To compare the effects of sodium bicarbonate and lactate for continuous veno-venous hemodiafiltration (CVVHDF) in critically ill patients. DESIGN AND SETTINGS: Prospective crossed-over controlled trial in the surgical and medical ICUs of a university hospital. PATIENTS: Eight patients with multiple organ dysfunction syndrome (MODS) requiring CVVHDF. INTERVENTION: Each patient received the two buffers in a randomized sequence over two consecutive days. MEASUREMENTS AND RESULTS: The following variables were determined: acid-base parameters, lactate production and utilization ((13)C lactate infusion), glucose turnover (6,6(2)H(2)-glucose), gas exchange (indirect calorimetry). No side effect was observed during lactate administration. Baseline arterial acid-base variables were equal with the two buffers. Arterial lactate (2.9 versus 1.5 mmol/l), glycemia (+18%) and glucose turnover (+23%) were higher in the lactate period. Bicarbonate and glucose losses in CVVHDF were substantial, but not lactate elimination. Infusing (13)C lactate increased plasma lactate levels equally with the two buffers. Lactate clearance (7.8+/-0.8 vs 7.5+/-0.8 ml/kg per min in the bicarbonate and lactate periods) and endogenous production rates (14.0+/-2.6 vs 13.6+/-2.6 mmol/kg per min) were similar. (13)C lactate was used as a metabolic substrate, as shown by (13)CO(2) excretion. Glycemia and metabolic rate increased significantly and similarly during the two periods during lactate infusion. CONCLUSION: Lactate was rapidly cleared from the blood of critically ill patients without acute liver failure requiring CVVHDF, being transformed into glucose or oxidized. Lactate did not exert undesirable effects, except moderate hyperglycemia, and achieved comparable effects on acid-base balance to bicarbonate.

Potential influence of the chemical composition of water on the stable oxygen isotope composition of continental ostracods

Many studies in continental areas have successfully used the oxygen isotope composition of fossil ostracod valves to reconstruct past hydrological conditions associated with large changes in climate. Yet, ostracods are known to crystallise their valves out of isotopic equilibrium for oxygen and they generally have higher 18O contents compared to inorganic calcite grown at equilibrium under the same condi- tions. A review of vital offsets determined for continental ostracods indicates that vital offsets might change from site to site, questioning a potential influence of environmental conditions on oxygen isotope fractionation in ostracods. Results from the literature suggest that pH has no influence on ostracod vital offset. A re-evaluation of results from Li and Liu (J Paleolimnol 43:111-120, 2010) suggests that salin- ity may influence oxygen isotope fractionation in ostracods, with lower vital offsets for higher salinities. Such a relationship was also observed for the vital offsets determined by Chivas et al. (The ostracoda- applications in quaternary research. American Geo- physical Union, Washington, DC, 2002). Yet, when results of all studies are compiled, the correlation between vital offsets and salinity is low while the correlation between vital offsets and host water Mg/Ca is higher, suggesting that ionic composition of water and/or relative abundance of major ions may also control oxygen isotope fractionation in ostracods. Lack of data on host water ionic composition for the different studies precludes more detailed examination at this stage. Further studies such as natural or laboratory cultures done under strictly controlled conditions are needed to better understand the potential influence of varying environmental condi- tions on oxygen isotope compositions of ostracod valves.

Urinary D-lactate excretion in infants receiving Lactobacillus johnsonii with formula.

BACKGROUND/AIMS: Supplementation with certain probiotics can improve gut microbial flora and immune function but should not have adverse effects. This study aimed to assess the risk of D-lactate accumulation and subsequent metabolic acidosis in infants fed on formula containing Lactobacillus johnsonii (La1). METHODS: In the framework of a double-blind, randomized controlled trial enrolling 71 infants aged 4-5 months, morning urine samples were collected before and 4 weeks after being fed formulas with or without La1 (1 x 10(8)/g powder) or being breastfed. Urinary D- and L-lactate concentrations were assayed by enzymatic, fluorimetric methods and excretion was normalized per mol creatinine. RESULTS: At baseline, no significant differences in urinary D-/L-lactate excretion among the formula-fed and breastfed groups were found. After 4 weeks, D-lactate excretion did not differ between the two formula groups, but was higher in both formula groups than in breastfed infants. In all infants receiving La1, urinary D-lactate concentrations remained within the concentration ranges of age-matched healthy infants which had been determined in an earlier study using the same analytical method. Urinary L-lactate also did not vary over time or among groups. CONCLUSIONS: Supplementation of La1 to formula did not affect urinary lactate excretion and there is no evidence of an increased risk of lactic acidosis.

Geochemical and H-O-Sr-Nd isotope evidence for magmatic processes and meteoric-water interactions in the basal complex of La Gomera, Canary Islands

The plutonic rocks of the Basal Complex of La Gomera, Canary Islands, Spain, were studied by means of major and trace element contents and by H-O-Sr-Nd isotope compositions in order to distinguish primary magmatic characteristics and late-stage alteration products. Deciphering the effects of alteration allowed us to determine primary, plume-related compositions that indicated D- and (18)O-depletion relative to normal upper mantle, supporting the conclusions of earlier studies on the plutonic rocks of Fuerteventura and La Palma. Late-stage alteration took place during the formation of the intrusive series induced by interaction with meteoric water. Inferred isotopic compositions of the meteoric water indicate that the water infiltrated into the rock edifice at a height of about 1500 m above sea level, suggesting the existence of a subaerial volcano which was active during the intrusive activity and that it has been either distroyed or remain buried by later volcanic and landslide events.

Salt-dependent renal effects of an angiotensin II antagonist in healthy subjects.

This study was designed to evaluate in healthy volunteers the renal hemodynamic and tubular effects of the orally active angiotensin II receptor antagonist losartan (DuP 753 or MK 954). Losartan or a placebo was administered to 23 subjects maintained on a high-sodium (200 mmol/d) or a low-sodium (50 mmol/d) diet in a randomized, double-blind, crossover study. The two 6-day diet periods were separated by a 5-day washout period. On day 6, the subjects were water loaded, and blood pressure, renal hemodynamics, and urinary electrolyte excretion were measured for 6 hours after a single 100-mg oral dose of losartan (n = 16) or placebo (n = 7). Losartan induced no significant changes in blood pressure, glomerular filtration rate, or renal blood flow in these water-loaded subjects, whatever the sodium diet. In subjects on a low-salt diet, losartan markedly increased urinary sodium excretion from 115 +/- 9 to 207 +/- 21 mumol/min (P < .05). The fractional excretion of endogenous lithium was unchanged, suggesting no effect of losartan on the early proximal tubule in our experimental conditions. Losartan also increased urine flow rate (from 10.5 +/- 0.4 to 13.1 +/- 0.6 mL/min, P < .05); urinary potassium excretion (from 117 +/- 6.9 to 155 +/- 11 mumol/min); and the excretion of chloride, magnesium, calcium, and phosphate. In subjects on a high-salt diet, similar effects of losartan were observed, but the changes induced by the angiotensin II antagonist did not reach statistical significance. In addition, losartan demonstrated significant uricosuric properties with both sodium diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Population demography of an endangered lizard, the Blue Mountains Water Skink.

BACKGROUND: Information on the age structure within populations of an endangered species can facilitate effective management. The Blue Mountains Water Skink (Eulamprus leuraensis) is a viviparous scincid lizard that is restricted to < 40 isolated montane swamps in south-eastern Australia. We used skeletochronology of phalanges (corroborated by mark-recapture data) to estimate ages of 222 individuals from 13 populations. RESULTS: These lizards grow rapidly, from neonatal size (30 mm snout-vent length) to adult size (about 70 mm SVL) within two to three years. Fecundity is low (mean 2.9 offspring per litter) and is affected by maternal body length and age. Offspring quality may decline with maternal age, based upon captive-born neonates (older females gave birth to slower offspring). In contrast to its broadly sympatric (and abundant) congener E. tympanum, E. leuraensis is short-lived (maximum 6 years, vs 15 years for E. tympanum). Litter size and offspring size are similar in the two species, but female E. leuraensis reproduce annually whereas many E. tympanum produce litters biennially. Thus, a low survival rate (rather than delayed maturation or low annual fecundity) is the key reason why E. leuraensis is endangered. Our 13 populations exhibited similar growth rates and population age structures despite substantial variation in elevation, geographic location and swamp size. However, larger populations (based on a genetic estimate of effective population size) contained older lizards, and thus a wider variance in ages. CONCLUSION: Our study suggests that low adult survival rates, as well as specialisation on a rare and fragmented habitat type (montane swamps) contribute to the endangered status of the Blue Mountains Water Skink.

First day of an oil spill on the open sea: early mass transfers of hydrocarbons to air and water.

During the first hours after release of petroleum at sea, crude oil hydrocarbons partition rapidly into air and water. However, limited information is available about very early evaporation and dissolution processes. We report on the composition of the oil slick during the first day after a permitted, unrestrained 4.3 m(3) oil release conducted on the North Sea. Rapid mass transfers of volatile and soluble hydrocarbons were observed, with >50% of ≤C17 hydrocarbons disappearing within 25 h from this oil slick of <10 km(2) area and <10 μm thickness. For oil sheen, >50% losses of ≤C16 hydrocarbons were observed after 1 h. We developed a mass transfer model to describe the evolution of oil slick chemical composition and water column hydrocarbon concentrations. The model was parametrized based on environmental conditions and hydrocarbon partitioning properties estimated from comprehensive two-dimensional gas chromatography (GC×GC) retention data. The model correctly predicted the observed fractionation of petroleum hydrocarbons in the oil slick resulting from evaporation and dissolution. This is the first report on the broad-spectrum compositional changes in oil during the first day of a spill at the sea surface. Expected outcomes under other environmental conditions are discussed, as well as comparisons to other models.

Bolus injections of synthetic atrial natriuretic peptide in patients with chronic renal failure or nephrotic syndrome.

The diuretic and natriuretic responses to exogenous synthetic atrial natriuretic peptide (ANP) were evaluated in patients with chronic renal failure (CRF) or nephrotic syndrome (NS). Patients were studied after an oral water load (8 ml/kg in CRF and 20 ml/kg in NS patients). A short intravenous bolus of either a placebo or ANP was administered when urine output was stable. In each group of patients, three doses of ANP were injected at 24 h intervals, i.e., 1.0, 1.5, and 2.0 micrograms/kg in the CRF and 1.0, 1.5, and 3.0 micrograms/kg in the NS group. Blood pressure and heart rate were monitored throughout the study and urinary volume and electrolyte excretion were measured every 20 min up to 3 h after the bolus. An acute and transient fall in blood pressure was observed immediately after the ANP injection. It was more pronounced in CRF than in NS patients. In CRF patients, ANP caused only a slight increase in urinary volume (13.5-44% over baseline) but a significant increase in urinary sodium excretion (45-114% over baseline). In NS patients, significant increases in both urine volume (60-105%) and sodium excretion (149-248%) were also found. In these latter patients, the renal response to ANP appeared to be better preserved. The hemodynamic and renal changes induced by ANP occurred mainly during the first 20 min following the ANP administration, when the peak plasma ANP levels were obtained. However, no clear dose-response effect could be evidenced in either group with the three doses of ANP chosen in this study.