Measurements of seismic attenuation and transient fluid pressure in partially saturated Berea sandstone: Evidence of fluid flow on the mesoscopic scale

A novel laboratory technique is proposed to investigate wave-induced fluid flow on the mesoscopic scale as a mechanism for seismic attenuation in partially saturated rocks. This technique combines measurements of seismic attenuation in the frequency range from 1 to 100?Hz with measurements of transient fluid pressure as a response of a step stress applied on top of the sample. We used a Berea sandstone sample partially saturated with water. The laboratory results suggest that wave-induced fluid flow on the mesoscopic scale is dominant in partially saturated samples. A 3-D numerical model representing the sample was used to verify the experimental results. Biot's equations of consolidation were solved with the finite-element method. Wave-induced fluid flow on the mesoscopic scale was the only attenuation mechanism accounted for in the numerical solution. The numerically calculated transient fluid pressure reproduced the laboratory data. Moreover, the numerically calculated attenuation, superposed to the frequency-independent matrix anelasticity, reproduced the attenuation measured in the laboratory in the partially saturated sample. This experimental?numerical fit demonstrates that wave-induced fluid flow on the mesoscopic scale and matrix anelasticity are the dominant mechanisms for seismic attenuation in partially saturated Berea sandstone.

Prograde mica 40Ar/39Ar growth ages recorded in high pressure rocks (Syros, Cyclades, Greece)

Phengites from the eclogite and blueschist-facies sequences of the Cycladic island of Syros (Greece) have been dated by the in situ UV-laser ablation Ar-40/Ar-39 method. A massive, phengite-rich eclogite and an omphacite-rich metagabbro were investigated. The phengites are eubedral and coarse-grained (several 100 mum), strain-free and exhibit no evidence for late brittle deformation or recrystallization. Apparent ages in these samples range from 43 to 50 Ma for the phengite-rich eclogite and 42 to 52 Ma for the ompbacitic metagabbro. This large spread of ages is visible at all scales-within individual grains as well as in domains of several 100 mum and across the entire sample (ca. 2 cm). Such variations have been traditionally attributed to metamorphic cooling or the incorporation of excess argon. However, the textural equilibrium between the phengites and other high pressure phases and the subtle compositional variations within the phengites, especially the preservation of growth textures, alternatively suggest that the observed range in ages may reflect variations of radiogenic argon acquired during phengite formation and subsequent growth, thus dating a discrete event on the prograde path. This implies that the oldest phengite 40Ar/39Ar ages provide the best estimate of a minimum crystallization age, which is in agreement with recently reported U-Pb and Lu-Hf geochronological data. Our results are consistent with available stable isotope data and further suggest that, under fluid-restricted conditions, both stable and radiogenic isotopic systems can survive without significant isotopic exchange during subduction and exhumation from eclogite-facies P-T conditions. (C) 2004 Elsevier B.V. All rights reserved.

Feasibility of non-invasive pressure support ventilation in infants with respiratory failure after extubation: a pilot study.

OBJECTIVE: To evaluate the feasibility and effects of non-invasive pressure support ventilation (NIV) on the breathing pattern in infants developing respiratory failure after extubation. DESIGN: Prospective pilot clinical study; each patient served as their own control. SETTING: A nine-bed paediatric intensive care unit of a tertiary university hospital. PATIENTS: Six patients (median age 5 months, range 0.5-7 months; median weight 4.2 kg, range 3.8-5.1 kg) who developed respiratory failure after extubation. INTERVENTIONS: After a period of spontaneous breathing (SB), children who developed respiratory failure were treated with NIV. MEASUREMENTS AND RESULTS: Measurements included clinical dyspnoea score (DS), blood gases and oesophageal pressure recordings, which were analysed for respiratory rate (RR), oesophageal inspiratory pressure swing (dPes) and oesophageal pressure-time product (PTPes). All data were collected during both periods (SB and NIV). When comparing NIV with SB, DS was reduced by 44% (P < 0.001), RR by 32% (P < 0.001), dPes by 45% (P < 0.01) and PTPes by 57% (P < 0.001). A non-significant trend for decrease in PaCO(2) was observed. CONCLUSION: In these infants, non-invasive pressure support ventilation with turbine flow generator induced a reduction of breathing frequency, dPes and PTPes, indicating reduced load of the inspiratory muscles. NIV can be used with some benefits in infants with respiratory failure after extubation.

Pulse pressure variation-guided fluid therapy after cardiac surgery: A pilot before-and-after trial.

PURPOSE: The aim of this study is to study the feasibility, safety, and physiological effects of pulse pressure variation (PPV)-guided fluid therapy in patients after cardiac surgery. MATERIALS AND METHODS: We conducted a pilot prospective before-and-after study during mandatory ventilation after cardiac surgery in a tertiary intensive care unit. We introduced a protocol to deliver a fluid bolus for a PPV ≥13% for at least >10 minutes during the intervention period. RESULTS: We studied 45 control patients and 53 intervention patients. During the intervention period, clinicians administered a fluid bolus on 79% of the defined PPV trigger episodes. Median total fluid intake was similar between 2 groups during mandatory ventilation (1297 mL [interquartile range 549-1968] vs 1481 mL [807-2563]; P = .17) and the first 24 hours (3046 mL [interquartile range 2317-3982] vs 3017 mL [2192-4028]; P = .73). After adjusting for several baseline factors, PPV-guided fluid management significantly increased fluid intake during mandatory ventilation (P = .004) but not during the first 24 hours (P = .47). Pulse pressure variation-guided fluid therapy, however, did not significantly affect hemodynamic, renal, and metabolic variables. No serious adverse events were noted. CONCLUSIONS: Pulse pressure variation-guided fluid management was feasible and safe during mandatory ventilation after cardiac surgery. However, its advantages may be clinically small.

Assessing the Functionality and Biocompatibility of a Wireless Contact Lens Sensor for 24 hour-intraocular Pressure Monitoring in Volunteers: Preliminary Results

Purpose: In vitro studies in porcine eyes have demonstrated a good correlation between induced intraocular pressure variations and corneal curvature changes, using a contact lens with an embedded microfabricated strain gauge. Continuous 24 hour-intraocular pressure (IOP) monitoring to detect large diurnal fluctuation is currently an unmet clinical need. The aims of this study is to evaluate precision of signal transmission and biocompatibility of 24 hour contact lens sensor wear (SENSIMED Triggerfish®) in humans. Methods: After full eye examination in 10 healthy volunteers, a 8.7 mm radius contact lens sensor and an orbital bandage containing a loop antenna were applied and connected to a portable recorder. Best corrected visual acuity and position, lubrication status and mobility of the sensor were assessed after 5 and 30 minutes, 4, 7 and 24 hours. Subjective comfort was scored and activities documented in a logbook. After sensor removal full eye examination was repeated, and the registration signal studied. Results: The comfort score was high and did not fluctuate significantly, except at the 7 hour-visit. The mobility of the contact lens was minimal but its lubrication remained good. Best corrected visual acuity was significantly reduced during the sensor wear and immediately after its removal. Three patients developed mild corneal staining. In all but one participant we obtained a registration IOP curve with visible ocular pulse amplitude. Conclusions: This 24 hour-trial confirmed the functionality and biocompatibility of SENSIMED Triggerfish® wireless contact lens sensor for IOP-fluctuation monitoring in volunteers. Further studies with a range of different contact lens sensor radii are indicated.

Novel acid phosphatase in Candida glabrata suggests selective pressure and niche specialization in the phosphate signal transduction pathway.

Evolution through natural selection suggests unnecessary genes are lost. We observed that the yeast Candida glabrata lost the gene encoding a phosphate-repressible acid phosphatase (PHO5) present in many yeasts including Saccharomyces cerevisiae. However, C. glabrata still had phosphate starvation-inducible phosphatase activity. Screening a C. glabrata genomic library, we identified CgPMU2, a member of a three-gene family that contains a phosphomutase-like domain. This small-scale gene duplication event could allow for sub- or neofunctionalization. On the basis of phylogenetic and biochemical characterizations, CgPMU2 has neofunctionalized to become a broad range, phosphate starvation-regulated acid phosphatase, which functionally replaces PHO5 in this pathogenic yeast. We determined that CgPmu2, unlike ScPho5, is not able to hydrolyze phytic acid (inositol hexakisphosphate). Phytic acid is present in fruits and seeds where S. cerevisiae grows, but is not abundant in mammalian tissues where C. glabrata grows. We demonstrated that C. glabrata is limited from an environment where phytic acid is the only source of phosphate. Our work suggests that during evolutionary time, the selection for the ancestral PHO5 was lost and that C. glabrata neofunctionalized a weak phosphatase to replace PHO5. Convergent evolution of a phosphate starvation-inducible acid phosphatase in C. glabrata relative to most yeast species provides an example of how small changes in signal transduction pathways can mediate genetic isolation and uncovers a potential speciation gene.

Blood pressure modifies the association between serum adiponectin and uric acid, in a sex-dependent manner

Purpose: Plasma adiponectin and serum uric acid (SUA) levels are negatively correlated. To better understand the possible mechanisms linking adiponectin and uric acid, we analyzed whether the association between adiponectin and SUA differed by hypertension status (or blood pressure level) and by sex. Methods and materials: We analyzed data from the populationbased CoLaus study (Switzerland). Fasting plasma adiponectin levels were assessed by ELISA and SUA by uricase-PAP. Blood pressure (BP) was measured using a validated automated device and hypertension was defined as having office BP 140/90 mm Hg or being on current antihypertensive treatment. Results: In the 2897 men and 3181 women, aged 35-74, BMI (mean ± SD) was 26.6 ± 4.0 and 25.1 ± 4.8 Kg/m2, systolic blood pressure (SBP) was 132.2 ± 16.6 and 124.8 ± 18.3 mm Hg, median (interquartile range) plasma adiponectin was 6.2 (4.1-9.2) and 10.6 (6.9-15.4) mg/dL, and hypertension prevalence was 42.0% and 30.2%, respectively. The age- and BMI- adjusted partial correlation coefficients between log-adiponectin and SUA were 0.09 and 0.06 in normotensive men and women (P <0.01), and 0.004 (P = 0.88) and 0.15 (P <0.001) in hypertensive men and women, respectively. In median regression adjusted for BMI, insulin, smoking, alcohol consumption, menopausal status and HDL-cholesterol, there was a significant three-way interaction between SUA, SBP and sex for their effect on adiponectin (dependent variable, P = 0.005), as well as interactions between SBP and sex (P = 0.014) and between SUA and sex (P = 0.033). Conclusion: Plasma adiponectin and SUA are negatively associated, independently of BMI and insulin, in a population-based study in Caucasians. However, BP modifies this inverse relationship, as it was significant mainly in women with elevated BP. This observation suggests that the link between adiponectin and SUA may be mediated by sex hormones and the hypertension status.

Direct Effect of Birth Weight on Childhood Blood Pressure: a Causal Mediation Analysis

Background: Numerous studies have shown a negative association between birth weight (BW) and blood pressure (BP) later in life. To estimate the direct effect of BW on BP, it is conventional to condition on current weight (CW). However, such conditioning can induce collider stratification bias in the estimate of the direct effect. Objective: To bound the potential bias due to U, an unmeasured common cause of CW and BP, on the estimate of the (controlled) direct effect of BW on BP. Methods: Data from a school based study in Switzerland were used (N = 4,005; 2,010 B/1,995 G; mean age: 12.3 yr [range: 10.1-14.9]). Measured common causes of BW-BP (SES, smoking, body weight, and hypertension status of the mother) and CW-BP (breastfeeding and child's physical activity and diet) were identified with DAGs. Linear regression models were fitted to estimate the association between BW and BP. Sensitivity analyses were conducted to assess the potential effect of U on the association between BW and BP. U was assumed 1) to be a binary variable that affected BP by the same magnitude in low BWand in normal BW children and 2) to have a different prevalence in low BW children and in normal BW children for a given CW. Results: A small negative association was observed between BW and BP [beta: -0.3 mmHg/kg (95% CI: -0.9 to 0.3)]. The association was strengthened upon conditioning for CW [beta: -1.5 mmHg/kg (95% CI: -2.1 to -0.9)]. Upon further conditioning on common causes of BW-BP and CW-BP, the association did not change substantially [beta: -1.4 mmHg/kg (95% CI: -2.0 to -0.8)]. The negative association could be explained by U only if U was strongly associated with BP and if there was a large difference in the prevalence of U between low BWand normal BW children. Conclusion: The observed negative association between BW and BP upon adjustment for CW was not easily explained by an unmeasured common cause of CWand BP.

A Variscan pressure-temperature-time path for the N-E Mont Blanc massif

The northeastern portion of the Mont Blanc massif in western Switzerland is predominantly comprised of the granitic rocks of the Mont Blanc intrusive suit, and the Mont Blanc basement gneisses. Within these metamorphic rocks are a variety of sub-economic Fe skarns. The mineral assemblages and fluid inclusions from these rocks have been used to derive age, pressure, temperature and fluid composition constraints for two Variscan events. Metamorphic hornblendes within the assemblages from the basement amphibolites and iron sk:lms have been dated using Ar-40/Ar-39, and indicate that these metamorphic events have a minimum age of approximately 334 Ma. Garnet-hornblende-plagioclase thermobarometry and stable isotope data obtained from the basement amphibolites are consistent with metamorphic temperatures in the range 515 to 580 degrees C, and pressures ranging from 5 to 8 kbar. Garnet-hornblende-magnetite thermobarometry and fluid inclusion studies indicate that the iron skarns formed at slightly lower temperatures, ranging from 400 to 500 degrees C in the presence of saline fluids at formational pressures similar to those experienced by the basement amphibolites. Late Paleozoic minimum uplift rates and geothermal gradients calculated using these data and the presence of Ladinien ichnofossils are on the order of 0.32 mm/year and 20 degrees C/km respectively. These uplift rates and geothermal gradients differ from those obtained from the neighbouring Aiguilles Rouges massif and indicate that these two massifs experienced different metamorphic conditions during the Carboniferous and Permian periods. During the early to late Carboniferous period the relative depths of the two massifs were reversed with the Aiguilles Rouges being initially unroofed at a much greater rate than the Mont Blanc, but experiencing relatively slower uplift rates near the termination of the Variscan orogeny.

Fast analysis of doping agents in urine by ultra-high-pressure liquid chromatography-quadrupole time-of-flight mass spectrometry I. Screening analysis.

The general strategy to perform anti-doping analyses of urine samples starts with the screening for a wide range of compounds. This step should be fast, generic and able to detect any sample that may contain a prohibited substance while avoiding false negatives and reducing false positive results. The experiments presented in this work were based on ultra-high-pressure liquid chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry. Thanks to the high sensitivity of the method, urine samples could be diluted 2-fold prior to injection. One hundred and three forbidden substances from various classes (such as stimulants, diuretics, narcotics, anti-estrogens) were analysed on a C(18) reversed-phase column in two gradients of 9min (including two 3min equilibration periods) for positive and negative electrospray ionisation and detected in the MS full scan mode. The automatic identification of analytes was based on retention time and mass accuracy, with an automated tool for peak picking. The method was validated according to the International Standard for Laboratories described in the World Anti-Doping Code and was selective enough to comply with the World Anti-Doping Agency recommendations. In addition, the matrix effect on MS response was measured on all investigated analytes spiked in urine samples. The limits of detection ranged from 1 to 500ng/mL, allowing the identification of all tested compounds in urine. When a sample was reported positive during the screening, a fast additional pre-confirmatory step was performed to reduce the number of confirmatory analyses.

Multiple introductions boosted genetic diversity in the invasive range of black cherry (Prunus serotina; Rosaceae).

BACKGROUND AND AIMS: Black cherry (Prunus serotina) is a North American tree that is rapidly invading European forests. This species was introduced first as an ornamental plant, then it was massively planted by foresters in many countries, but its origins and the process of invasion remain poorly documented. Based on a genetic survey of both native and invasive ranges, the invasion history of black cherry was investigated by identifying putative source populations and then assessing the importance of multiple introductions on the maintenance of gene diversity. METHODS: Genetic variability and structure of 23 populations from the invasive range and 22 populations from the native range were analysed using eight nuclear microsatellite loci and five chloroplast DNA regions. KEY RESULTS: Chloroplast DNA diversity suggests there were multiple introductions from a single geographic region (the north-eastern United States). A low reduction of genetic diversity was observed in the invasive range for both nuclear and plastid genomes. High propagule pressure including both the size and number of introductions shaped the genetic structure in Europe and boosted genetic diversity. Populations from Denmark, The Netherlands, Belgium and Germany showed high genetic diversity and low differentiation among populations, supporting the hypothesis that numerous introduction events, including multiple individuals and exchanges between sites, have taken place during two centuries of plantation. CONCLUSIONS: This study postulates that the invasive black cherry has originated from east of the Appalachian Mountains (mainly the Allegheny plateau) and its invasiveness in north-western Europe is mainly due to multiple introductions containing high numbers of individuals.

Predictive Factors for Intraocular Pressure Reduction after Phacoemulsification in Swiss Patients.

Background: Phacoemulsification is known to induce postoperative intraocular pressure (IOP) reduction, the degree of which varies according to glaucoma subtype and race. The authors set out to investigate the effect of cataract surgery on IOP, in a Swiss Caucasian population, and identify ocular predictive factors. Patients and Methods: 234 consecutive cases of 188 patients undergoing phacoemulsification between January 2011 and December 2012 were retrospectively reviewed and data collected. Exclusion criteria included acute angle closure, malignant glaucoma and pre-existing or subsequent glaucoma surgery. Pre- and post-operative visual acuity, IOP, gonioscopic findings, glaucoma medications, and laser treatments were recorded for eligible eyes. All eyes received the same postoperative regimen. Using multivariate analysis the predictive power of preoperative IOP, iridocorneal angle width, axial length on IOP reduction following phacoemulsification at months 3, 6 and 12 postoperatively were assessed. Eyes with narrow angles were compared against those with open angles. Results: 172 eyes of 121 patients met the inclusion criteria; mean age was 70.3 years (SD ± 10.7 years), with 77 males. Preoperatively median IOP was 16 mmHg (range 9-32 mmHg), mean number of glaucoma medications was 1.2 (SD ± 1.1), median visual acuity was 0.28 LogMAR (range 0-2.3LogMar). At 3 months post-operatively mean IOP decreased to 14 mmHg (p < 0.01) and remained statistically significantly reduced until 12 months, mean number of glaucoma medications was reduced to 1.0 and mean Snellen visual acuity increased to 0.8. Multivariate analysis revealed that pre-operative IOP and iridocorneal angle width (at 3 months) were significant predictive indicators of IOP reduction. At 12 months, IOP reduction was similar between open and narrow angle groups and total IOP reduction was no longer statistically significant. No intraoperative complications were recorded. Conclusions: Intraocular pressure reduction following phacoemulsification was greatest during the very early post-operative period, particularly in narrow angle patients. By one year, angle size was no longer predictive of IOP lowering, however pre-operative IOP and number of anti-glaucoma medications remained correlated with total IOP reduction.

Renal sodium handling and nighttime blood pressure.

Blood pressure follows a circadian rhythm with a physiologic 10% to 20% decrease during the night. There is now increasing evidence that a blunted decrease or an increase in nighttime blood pressure is associated with a greater prevalence of target organ damage and a faster disease progression in patients with chronic kidney diseases. Several factors contribute to the changes in nighttime blood pressure including changes in hormonal profiles such as variations in the activity of the renin-angiotensin and the sympathetic nervous systems. Recently, it was hypothesized that the absence of a blood pressure decrease during the nighttime (nondipping) is in fact a pressure-natriuresis mechanism enabling subjects with an impaired capacity to excrete sodium to remain in sodium balance. In this article, we review the clinical and epidemiologic data that tend to support this hypothesis. Moreover, we show that most, if not all, clinical conditions associated with an impaired dipping profile are diseases associated either with a low glomerular filtration rate and/or an impaired ability to excrete sodium. These observations would suggest that renal function, and most importantly the ability to eliminate sodium during the day, is indeed a key determinant of the circadian rhythm of blood pressure.

Metoprolol prevents sodium retention induced by lower body negative pressure in healthy men.

BACKGROUND: Lower body negative pressure (LBNP) has been shown to induce a progressive activation of neurohormonal systems, and a renal tubular and hemodynamic response that mimics the renal adaptation observed in congestive heart failure (CHF). As beta-blockers play an important role in the management of CHF patients, the effects of metoprolol on the renal response were examined in healthy subjects during sustained LBNP. METHODS: Twenty healthy male subjects were randomized in this double blind, placebo versus metoprolol 200 mg once daily, study. After 10 days of treatment, each subject was exposed to 3 levels of LBNP (0, -10, and -20 mbar) for 1 hour, each level of LBNP being separated by 2 days. Neurohormonal profiles, systemic and renal hemodynamics, as well as renal sodium handling were measured before, during, and after LBNP. RESULTS: Blood pressure and heart rate were significantly lower in the metoprolol group throughout the study (P < 0.01). GFR and RPF were similar in both groups at baseline, and no change in renal hemodynamic values was detected at any level of LBNP. However, a reduction in sodium excretion was observed in the placebo group at -20 mbar, whereas no change was detected in the metoprolol group. An increase in plasma renin activity was also observed at -20 mbar in the placebo group that was not observed with metoprolol. CONCLUSION: The beta-blocker metoprolol prevents the sodium retention induced by lower body negative pressure in healthy subjects despite a lower blood pressure. The prevention of sodium retention may be due to a blunting of the neurohormonal response. These effects of metoprolol on the renal response to LBNP may in part explain the beneficial effects of this agent in heart failure patients.

Ambulatory blood pressure monitoring in adolescent untreated hypertensive patients.

Ambulatory blood pressure profiles were obtained with the portable semi-automatic blood pressure recorder Remler M2000 in groups of 20 adolescents, 20 young and 20 middle-aged adults and 20 elderly untreated patients, all considered by their physician to be hypertensive. It was found that adolescents who are hypertensive when seeing their physician are more often normotensive outside the physician's office than adult and elderly patients under similar conditions. The increased heart rate variability which was detected in adolescents was not associated with an enhanced blood pressure variability.