Experimental demonstration of optical stochastic cooling.

Particle accelerators and storage rings have been transformative instruments of discovery, and, for many applications, innovations in particle-beam cooling have been a principal driver of that success1. Stochastic cooling (SC), one of the most important conceptual and technological advances in this area2-6, cools a beam through granular sampling and correction of its phase-space structure, thus bearing resemblance to a 'Maxwell's demon'. The extension of SC from the microwave regime up to optical frequencies and bandwidths has long been pursued, as it could increase the achievable cooling rates by three to four orders of magnitude and provide a powerful tool for future accelerators. First proposed nearly 30 years ago, optical stochastic cooling (OSC) replaces the conventional microwave elements of SC with optical-frequency analogues and is, in principle, compatible with any species of charged-particle beam7,8. Here we describe a demonstration of OSC in a proof-of-principle experiment at the Fermi National Accelerator Laboratory's Integrable Optics Test Accelerator9,10. The experiment used 100-MeV electrons and a non-amplified configuration of OSC with a radiation wavelength of 950 nm, and achieved strong, simultaneous cooling of the beam in all degrees of freedom. This realization of SC at optical frequencies serves as a foundation for more advanced experiments with high-gain optical amplification, and advances opportunities for future operational OSC systems with potential benefit to a broad user community in the accelerator-based sciences.

Amplification of flat laser pulse train.

We present modeling and measurements of flattop amplification of a laser pulse train in a diode pumped Nd:YLF system. We establish a theoretical model, accounting for the transverse Gaussian shape of an amplified laser beam, in order to explain remaining slopes in the pulse train energy. The influence of the transverse Gaussian shape on the train's flatness has been experimentally verified. Based on the model we are able to increase the total amplification of a long train of infrared seed beam in the drive laser system at the Fermilab Accelerator Science and Technology facility. The single-pass amplifier improvements resulted in a gain of ∼7 with flat output pulse train for up to 1000 seed pulses.

Reduced exhaled NO is related to impaired nasal potential difference in patients with cystic fibrosis.

Nitric oxide (NO) plays a central role in many airway physiological functions, and its production appears to be related with progression of lung disease in patients with cystic fibrosis (CF). However, underlying mechanisms which specifically link NO and CF-related lung disease remain unclear. Following in vitro and animal studies suggesting a role for NO in ion transport in various epithelia, this work investigates the relationship between transepithelial baseline potential difference (BPD), an index of airway ion transport, and exhaled NO in the airways of adult patients with CF. Association with other phenotypic traits, lung function tests and CFTR genotype was also assessed. Using simple linear regression, F(E)NO and transepithelial BPD values were significantly inversely correlated (p<0.001, r=-0.53). Polynomial analysis evidenced an asymptotic relationship between F(E)NO and BPD values, yielding a plateau for absolute BPD values above 50 mV. This relation was not altered by adjustment for clinical and genetic characteristics of the patients. The relationship between exhaled NO and transepithelial BPD suggests that low NO concentrations likely worsens airway ion transport impairment resulting from CFTR defect. These results fit with experimental studies that suggest the inhibitory effect of NO on sodium absorption, which is the main determinant of airway basal transepithelial conductance.

Extracorporeal carbon dioxide removal and low-frequency positive-pressure ventilation. Improvement in arterial oxygenation with reduction of risk of pulmonary barotrauma in patients with adult respiratory distress syndrome.

Mortality of the adult respiratory distress syndrome (ARDS) remains high and could be increased by pulmonary barotrauma induced by positive-pressure mechanical ventilation. Extracorporeal CO2 removal combined with low-frequency positive-pressure ventilation (ECCO2R-LFPPV) has been proposed to reduce lung injury while supporting respiratory failure. Use of this technique in 23 patients resulted in the following: a dramatic and highly significant increase of PaO2 obtained rapidly with ECCO2R-LFPPV, allowing subsequent reduction in inspired oxygen fraction; a reduction of the risk of barotrauma evidenced by a significant decrease in pressures and insufflated volumes; a survival rate of 50 percent. Bleeding was the only complication related to the technique and was the cause of death in four patients. This method allowed improvement in gas exchange along with reduction of the risk of barotrauma caused by the ventilator.

Accuracy assessment for three fiberoptic pulmonary artery catheters for SvO2 monitoring.

OBJECTIVE: To compare values of SvO2 obtained by reflectance spectrophotometry continuous monitoring with those obtained from blood samples measurements by transmission spectrophotometry (Co-Oximetry). DESIGN: Values of SvO2 recorded by three pulmonary artery catheters for continuous monitoring, SAT1, SAT2 and Oximetrix3 (OX3), were compared in a prospective manner to those measured on blood samples by a Co-Oximeter, using the statistical analysis of Bland and Altman. SETTING: Adult intensive care unit in an University Hospital. PATIENTS: 37 patients admitted for acute respiratory failure and/or shock who required hemodynamic monitoring. MAIN RESULTS: The bias (average under- or overestimation) was small for all comparative measurements: +1.3, -0.2 and +1.0 sat% for SAT1, SAT2 and OX3, respectively. However, limits of agreement were only acceptable for SAT2 (-8.3 to +7.9 sat%) and OX3 (-6.7 to +8.6 sat%), but not for SAT1 (-23.3 to +25.9 sat%). No significant drift during 24 h was found with the three catheters. However, in vitro calibration was only found acceptable for SAT2 and OX3. The results were not influenced by the numbers of wavelengths of the device (2 for SAT1 and SAT2, and 3 for OX3) nor did they correlate with any of the hemodynamic and biochemical variables tested. CONCLUSION: For usual monitoring in the ICU, SAT2 and OX3, gave SvO2 values which are in acceptable agreement with SvO2 measured on blood samples by Co-Oximetry.

Association of PEEP with two different inflation volumes in ARDS patients: effects on passive lung deflation and alveolar recruitment.

OBJECTIVE: To assess the effects of the association of positive end-expiratory pressure (PEEP) with different inflation volumes (V(T)'s) on passive lung deflation and alveolar recruitment in ARDS patients. DESIGN: Clinical study using PEEP with two different V(T)'s and analyzing whether passive lung deflation and alveolar recruitment (Vrec) depend on end-inspired (EILV) or end-expired (EELV) lung volume in mechanically ventilated ARDS patients. SETTING: Medical intensive care unit in a university hospital. PATIENTS AND PARTICIPANTS: Six mechanically ventilated consecutive supine patients with ARDS. INTERVENTIONS: Time-course of thoracic volume decay during passive expiration and Vrec were investigated in six ARDS patients ventilated on PEEP with baseline V(T) (V(T),b) and 0.5V(T) (0.5V(T),b), and on zero PEEP (ZEEP) with V(T),b. Time constants of the fast (tau1) and slow (tau2) emptying compartments, as well as resistances and elastances were also determined. MEASUREMENTS AND RESULTS: (a) the biexponential model best fitted the volume decay in all instances. The fast compartment was responsible for 84+/-7 (0.5V(T),b) and 86+/-5% (V(T),b) on PEEP vs 81+/-6% (V(T),b) on ZEEP (P:ns) of the exhaled V(T), with tau1 of 0.50+/-0.13 and 0.58+/-0.17 s vs 0.35+/-0.11 s, respectively; (b) only tau1 for V(T),b on PEEP differed significantly (P < 0.02) from the one on ZEEP, suggesting a slower initial emptying; (c) for the same PEEP, Vrec was higher with a higher volume (V(T)b) than at a lesser one (0.5V(T),b), reflecting the higher V(T). CONCLUSIONS: In mechanically ventilated ARDS patients: (a) the behavior of airway resistance seems to depend on the degree of the prevailing lung distension; (b) alveolar recruitment appears to be more important when higher tidal volumes are used during mechanical ventilation on PEEP; (c) PEEP changes the mechanical properties of the respiratory system fast-emptying compartment.

Mechanical effects of PEEP in patients with adult respiratory distress syndrome.

In 10 patients with adult respiratory distress syndrome, we studied the effects on respiratory system mechanics of two levels of positive end-expiratory pressure (PEEP), best PEEP (BP) and half of this value (HBP), using a respiratory inductive plethysmograph (RIP) combined with a super syringe. We found the following. 1) Inflation compliance of pressure-volume (PV) curves did not change significantly. 2) End-expiratory volume increased with HBP and further with BP (278 +/- 186 and 464 +/- 313 ml, respectively, P less than 0.01). This increase was positively correlated with inflation compliance for HBP and BP (r = 0.794, P less than 0.01 and r = 0.876, P less than 0.01, respectively). 3) No dynamic hyper-inflation was detected on mechanical ventilation at zero end-expiratory pressure (ZEEP), and the time constant of the respiratory system was in the normal range (0.79 +/- 0.21 s). 4) Hysteresis of PVrip curves, which were corrected for gas exchange, decreased significantly with PEEP (P less than 0.05). We conclude that PEEP does not change inflation PV curve but induces an increase in intrathoracic volume whose magnitude is related to compliance and PEEP level. The reduction of hysteresis with PEEP suggests less gas trapping and thus a functional improvement.

Causes of error of respiratory pressure-volume curves in paralyzed subjects.

Respiratory pressure-volume (PV) curves are commonly obtained in paralyzed patients by relating airway pressure to volume changes of a syringe (Vsyr). This is based on the implicit assumption that changes in thoracic volume (Vtho) and Vsyr are equal. We undertook to verify this assumption through simultaneous measurements of Vtho by respiratory inductive plethysmography and Vsyr in six comatose, paralyzed, intubated patients. At any constant Vsyr, Vtho fell and was smaller on deflation than on inflation during inflation-deflation (ID) cycle. The rate of fall was 110 +/- 64 (SD) ml/min. During ID cycles lasting 76 +/- 7 s, thoracic PV curves showed less hysteresis and a larger compliance on deflation than PVsyr curves (12 +/- 2 vs. 18 +/- 6% and 73 +/- 13 vs. 67 +/- 12 ml/cmH2O, P less than 0.05). With PVsyr curves, hysteresis increased and compliance on deflation decreased with increasing rate of fall of Vtho. We submit that the difference between changes in Vsyr and Vtho is best explained by gas exchange and should be taken into account when performing PV curves with a syringe in paralyzed patients.

Increased nitric oxide in exhaled air in patients with systemic sclerosis.

OBJECTIVE: To assess the lung production of nitric oxide (NO) in patients with systemic sclerosis. METHODS: The NO concentration and its rate of production by the lungs were measured in the exhaled air in 14 patients with systemic sclerosis and in 12 healthy control subjects using the chemiluminescent method. RESULTS: The NO concentration and its rate of production were significantly increased in scleroderma patients (mean +/- SEM, 18.7 +/- 1.7 ppb and 5.8 +/- 0.5 nmol/min, respectively), as compared with control subjects (11.2 +/- 0.8 ppb and 4.3 +/- 0.4 nmol/min, p < 0.01 and p < 0.05, respectively). CONCLUSION: The pulmonary production of NO is increased in scleroderma patients, which might reflect and contribute to the inflammatory processes of the lungs in systemic sclerosis.

Effects of muscimol or homotaurine on sleep-wake states in alcohol-dependent rats during withdrawal.

Sleep-wake states were studied following withdrawal in 36 adult male wistar alcohol-dependent rats, after chronic administration of ethanol (10 g/kg/24 h) for 13 days. In the light phase of the withdrawal day, 12 alcohol-dependent rats received muscimol (0.25 mg/kg), 12 received homotaurine (140 mg/kg), and 12 received 0.9% physiological saline (10 ml/kg). The results have been compared with a control group of 36 rats that received water during the treatment phase of the experiment, and the 14th day received intraperitoneal muscimol or homotaurine. Muscimol significantly improves the alterations of sleep-wake states in alcohol-withdrawn rats, decreasing the percentage of active wakefulness and increasing the percentage of REMS, but without any action on the latency of appearance of REMS, which remains shortened. The effects of homotaurine are less important on the wakefulness, but it also increases the percentage of REMS without influencing its latency of appearance. The influence of these GABA(A) agonists is not identical during the whole period of survey in the light phase, as there are important differences in the temporal sequences for each of them. We conclude that the stimulation of GABA(A) receptors, of which the activity is decreased during alcohol withdrawal, significantly improves the disturbances in the sleep-wake states in the alcohol-dependent rats, in a time-related manner, and there are significant pharmacodynamic differences between muscimol and homotaurine.

Comparison of transesophageal echocardiographic, fick, and thermodilution cardiac output in critically ill patients.

PURPOSE: Recent observations have highlighted errors in the thermodilution technique of measuring cardiac output. Thus, cardiac output measurements using transesophageal echocardiography and the Fick method were compared with simultaneous thermodilution measurements. METHODS: In 13 mechanically ventilated critically ill patients, cardiac output was determined simultaneously using (1) transesophageal echocardiography (COTEE, (2) the Fick method (COFICK, and (3) thermodilution (COTD immediately before and after a rapid infusion of 500 mL of saline. Left ventricular end-diastolic and end-systolic areas were measured using the transesophageal echocardiographic transgastric short axis view, and COTEE was calculated from the corresponding volumes. Absolute cardiac output values and the changes from before to after saline infusion (delta CO) were compared using analysis of variance, linear regression, and the Bland and Altman method. RESULTS: There were no significant differences between COTEE (8.0 +/- 3.4), COFICK (8.4 +/- 3.3), and COTD (8.3 +/- 3.0) or between delta COTEE, delta COFICK, and delta COTD using analysis of variance. However, correlations between COTEE and COTD (r2 = 0.46; P < .00001), COFICK and COTD (r2 = 0.46; P < .0001), and COTEE and COFICK (r2 = 0.42; P < .0001) were only moderately good. Using the method of Bland and Altman, the mean difference (+/-2 standard deviations) between COTEE and COTD was 0.3 +/- 4.3 L/min, between COFICK and COTD was -1.0 +/- 3.8 L/min, and between COTEE and COFICK was 0.6 +/- 5.6 L/min, whereas the difference between delta COTEE and delta COTD was 0% +/- 26%, between delta COFICK and delta COTD was 9% +/- 46%, and between delta COTEE and delta COFICK was 8% +/- 39%. CONCLUSIONS: There are substantial differences in cardiac output as measured by these three methods, best demonstrated using the method of Bland and Altman. The variability of cardiac output and its derivatives (eg, oxygen delivery) should be borne in mind when making clinical decisions on individual patients.

[A surveillance method for products used by drug addicts examined in emergency units]. / Essai de mise au point d'une méthode de surveillance des produits utilisés par les toxicomanes consultant dans les services d'accueil.

Products used in a toxicomaniac way are in rapid change, and different from different area. Users too have to be better known. Authors present a simple survey method of these products, based on sample use. First results seem to be correct. These method may be used, associated with others, in a network as those existent for many years in the United States.

[Observation of illicit or misused psychotropic drugs (O.P.P.I.D.U.M.): five years of surveillance of products consumed by drug addicts at Marseille]. / Observation des produits psychotropes illicites ou détournés de leur utilisation médicamenteuse (O.P.P.I.D.U.M.): cinq ans de surveillance des produits consommés par les toxicomanes à Marseille.

The aim of O.P.P.I.D.U.M. is the survey of products used by drug addicts. A five year survey, based on regular pools, has provided interesting results. 1,283 patients (80 per cent men, about 27 years old, 1/4 employed) used 2,241 drugs. The most frequent was heroin, followed by benzodiazepines, cannabis and cocaine. Flunitrazepam was the most commonly misused product, taken by users who started consumption earlier, with a higher rate of unemployment and imprisonment. Cocaine was as often taken intravenously as by sniffing, and most often used before imprisonment. Ecstasy (M.D.M.A.) has appeared recently. Codeine taken alone was used by subjects older than the heroin users, more frequently employed and virtually never prison inmates: this suggests the existence of an unofficial detoxication and substitution process. Confidence of clinicians needs anonymity of the records and return of information. Such a campaign is about to be launched.

[In vitro study of the modulation of human ureteral tonus by nitric oxide and zaprinast, a phosphodiesterase inhibitor]. / Etude in vitro de la modulation du tonus urétéral humain par le monoxyde d'azote et un inhibiteur des phosphodiestérases, le zaprinast.

AIM OF THE STUDY: To assess the role of nitric oxide (NO) and its second messenger, cGMP, on the mechanisms underlying human ureteral smooth muscle relaxation. METHODS: Proximal segments of ureter were dissected from nephrectomy, then cut into rings and suspended in organ chambers. Isometric tone was recorded at baseline and after preincubation with KCl (120 mumol). The Increasing concentration (10-8-10-4 M) of NO donors, Sodium nitroprusside, (SNP) and molsidomine (SIN-1) and a type V phosphodiesterase inhibitor, Zaprinast were added to the organ chambers and a dose response curve was constructed from each experiment. RESULTS: Dose-dependent relaxation was seen with all compounds. This was, however, more pronounced with SNP as compared with SIN-1. Zaprinast alone had marginal relaxant effect but markedly potentiated the relaxing effect of the NO donor SNP (p < 0.05). Inhibition of NO synthesis by the arginine analogue L-NA increased electrical-induced contraction (98 +/- 4% vs 122 +/- 3%, p < 0.001). CONCLUSION: Activation of the soluble guanylate cyclase by NO donors markedly relaxed significantly human ureteral smooth muscle but inhibition of phosphodiesterase did not affect the in vitro relaxation. Our results suggest that cGMP is an important second messenger in the transduction signalling pathway leading to relaxation of human ureteral smooth muscle. By contrast, basal activity of phosphodiesterase seems to be marginal under physiological condition.

Methods for characterizing magnetic footprints of perpendicular magnetic recording writer heads.

In this work, the magnetic footprints, along with some of its dynamic features in recording process, of perpendicular magnetic recording writer heads have been characterized by using three different techniques. Those techniques are the spin-stand stationary footprint technique, the spin-stand dynamic footprint technique, and the coherent writing technique combined with magnetic force microscope imaging method. The characteristics of those techniques have been compared to one another. It was found experimentally that the spin-stand stationary method could not precisely catch some peculiar recording dynamics of the write heads in certain conditions. The advantages and disadvantages among all those techniques are also examined and discussed in detail.

Demonstration of a real-time interferometer as a bunch-length monitor in a high-current electron beam accelerator.

A real-time interferometer (RTI) has been developed to monitor the bunch length of an electron beam in an accelerator. The RTI employs spatial autocorrelation, reflective optics, and a fast response pyro-detector array to obtain a real-time autocorrelation trace of the coherent radiation from an electron beam thus providing the possibility of online bunch-length diagnostics. A complete RTI system has been commissioned at the A0 photoinjector facility to measure sub-mm bunches at 13 MeV. Bunch length variation (FWHM) between 0.8 ps (~0.24 mm) and 1.5 ps (~0.45 mm) has been measured and compared with a Martin-Puplett interferometer and a streak camera. The comparisons show that RTI is a viable, complementary bunch length diagnostic for sub-mm electron bunches.