Carotid Doppler flowmetry correlates poorly with thermodilution cardiac output following cardiac surgery.

BACKGROUND: It remains unclear whether measuring carotid arterial flow by the time velocity integral using vascular Doppler ultrasound can be used to monitor cardiac output and volume responsiveness. METHODS: The carotid Doppler flow (time velocity integral and peak flow velocity variation) was assessed in triplicate by an intensivist with formal vascular ultrasound training. Thirty-three patients admitted following coronary by-pass surgery were studied before and after a passive leg-raising manoeuvre to investigate volume responsiveness (more than 10% increase in cardiac output) along with indices of arterial load measuring cardiac output by thermodilution. Pearson's correlation coefficient and area under the curve (AUC) by receiver operating characteristics were calculated. RESULTS: A significant correlation between carotid Doppler flow and cardiac output was demonstrated in post-operative cardiac surgery patients (r = 0.80 [95%CI 0.61-0.89]), including relative changes following passive leg raising (r = 0.79 [95%CI 0.60-0.89]) that showed a mean difference of 2% with wide limits of agreements (-19% to 16%). Changes in carotid Doppler flow following passive leg raising correlated with the baseline arterial resistance but not with compliance or effective elastance. A peak flow variation > 10% before passive leg raising discriminated responders to the manoeuvre with an AUC of 0.81 [95% CI 0.55-0.95]. CONCLUSIONS: Weak correlations between common carotid Doppler flow and cardiac output mean that the methods cannot be used interchangeably in post-operative cardiac surgery patients.

[Alcohol use in young adolescents. A survey in French secondary schools]. / Consommation d'alcool chez les jeunes adolescents : enquête en milieu scolaire.

Among young adolescents, early use of alcohol has been shown to be related to later alcohol use disorders and alcohol-related problems in numerous epidemiologic studies. However, if drinking problems are now well documented in young people, few data are available on alcohol use in children and young adolescents. The purpose of this study was to examine the perceptions and attitudes with respect to alcohol use among young adolescents entering their first year of secondary school (mean age, 11.5 years). Data were collected from the ESPACE program, a preventive program conducted in the educational district of Limoges, France. Of the 2268 respondents with complete data, 73.4% (77.1% in males vs. 69.9% in females; P<0.001) reported having tasted alcohol drinks and 3.7% (4.9% in males vs. 2.6% in females; P=0.004) having experienced drunkenness at least once. Of these adolescents, 5.4% (8.5% in males vs. 2.4% in females, P<0.001) reported consuming alcohol at least once per month, which may be considered as a sort of regular drinking pattern. Taking age, sex, and level of alcohol consumption into account, experience of drunkenness (21.9% in regular users vs. 3.7% in occasional users), tobacco use (25.8% in regular users vs. 12.6% in occasional users and 1.5% in nonusers) and cannabis use (6.0% in regular users vs. 0.9% in occasional users and 0.2% in nonusers) were found to be significantly more frequent in regular alcohol users than in other students (P<0.001). Data analysis also showed that regular alcohol users felt significantly more frequently depressed, lacking self-assurance, dissatisfied with their physical appearance and their way of life, and they felt that they exhibited significantly more impairments in their interactions with parents, peers, and the school environment. Similarly, they were found to have significantly more frequently an inclination for risk behaviors and a significantly more positive view of drinking than other students. These results look almost like those reported in adolescents and young people, and show that the alcohol abuse pattern is drawn early in childhood. They also highlight the value of epidemiologic investigations for planning preventive interventions.

The Bionanoprobe: hard X-ray fluorescence nanoprobe with cryogenic capabilities.

Hard X-ray fluorescence microscopy is one of the most sensitive techniques for performing trace elemental analysis of biological samples such as whole cells and tissues. Conventional sample preparation methods usually involve dehydration, which removes cellular water and may consequently cause structural collapse, or invasive processes such as embedding. Radiation-induced artifacts may also become an issue, particularly as the spatial resolution increases beyond the sub-micrometer scale. To allow imaging under hydrated conditions, close to the `natural state', as well as to reduce structural radiation damage, the Bionanoprobe (BNP) has been developed, a hard X-ray fluorescence nanoprobe with cryogenic sample environment and cryo transfer capabilities, dedicated to studying trace elements in frozen-hydrated biological systems. The BNP is installed at an undulator beamline at sector 21 of the Advanced Photon Source. It provides a spatial resolution of 30 nm for two-dimensional fluorescence imaging. In this first demonstration the instrument design and motion control principles are described, the instrument performance is quantified, and the first results obtained with the BNP on frozen-hydrated whole cells are reported.

An in-vacuum x-ray diffraction microscope for use in the 0.7-2.9 keV range.

A dedicated in-vacuum coherent x-ray diffraction microscope was installed at the 2-ID-B beamline of the Advanced Photon Source for use with 0.7-2.9 keV x-rays. The instrument can accommodate three common implementations of diffractive imaging; plane wave illumination; defocused-probe (Fresnel diffractive imaging) and scanning (ptychography) using either a pinhole, focused or defocused probe. The microscope design includes active feedback to limit motion of the optics with respect to the sample. Upper bounds on the relative optics-to-sample displacement have been measured to be 5.8 nm(v) and 4.4 nm(h) rms/h using capacitance micrometry and 27 nm/h using x-ray point projection imaging. The stability of the measurement platform and in-vacuum operation allows for long exposure times, high signal-to-noise and large dynamic range two-dimensional intensity measurements to be acquired. Finally, we illustrate the microscope's stability with a recent experimental result.

A dynamic network simulation of the nematode tap withdrawal circuit: predictions concerning synaptic function using behavioral criteria.

The nematode tap withdrawal reflex demonstrates several forms of behavioral plasticity. Although the neural connectivity that supports this behavior is identified (Integration of mechanosensory stimuli in Caenorhabditis elegans, Wicks and Rankin, 1995, J Neurosci 15:2434-2444), the neurotransmitter phenotypes, and hence whether the synapses in the circuit are excitatory or inhibitory, remain uncharacterized. Here we use a novel strategy to predict the polarity configuration, i.e., the array of excitatory and inhibitory connections, of the nematode tap withdrawal circuit using an anatomically and physiologically justifiable dynamic network simulation of that circuit. The output of the modeled circuit was optimized to the behavior of animals, which possessed circuits altered by surgical ablation by exhaustively enumerating an array of synaptic signs that constituted the modeled circuit. All possible polarity configurations were then compared, and a statistical analysis was used to determine whether, for a given synaptic class, a particular polarity was associated with a good fit to behavioral data. The results from four related experiments were used to predict the polarities of seven of the nine cell classes of the tap withdrawal circuit. In addition, the model was used to assess possible roles for two novel mechanosensory integration neurons: DVA and PVD.

A national econometric forecasting model of the dental sector.

The Econometric Model of the the Dental Sector forecasts a broad range of dental sector variables, including dental care prices; the amount of care produced and consumed; employment of hygienists, dental assistants, and clericals; hours worked by dentists; dental incomes; and number of dentists. These forecasts are based upon values specified by the user for the various factors which help determine the supply an demand for dental care, such as the size of the population, per capita income, the proportion of the population covered by private dental insurance, the cost of hiring clericals and dental assistants, and relevant government policies. In a test of its reliability, the model forecast dental sector behavior quite accurately for the period 1971 through 1977.