Distensibility Differs Between Sall Arteries and Veins in the Newborn Piglet Lung

BACKGROUND: We previously used micro-CT techniques to measure pulmonary artery distensibility in 3 week old piglets. Pressure/diameter relationships were measured for each artery and the slope (a) was then plotted against its diameter intercept at 0 pressure (Do). The resultant diameter independent distensibility parameter, a, was estimated by linear regression to be 1.6% per mmHg for arteries between 0.2 and 3.0 mm Do. OBJECTIVE: This study sought to determine whether; 1) distensibility of smaller arteries was similar to that of arteries with Do\u3e 0.2 mm; and 2) whether small vein and artery distensibility was similar. DESIGN/METHODS: Lower lobes were isolated and perfused with papaverine/saline to remove blood and tone. Lobar bronchi were cannulated and lobes inflated to 3 mmHg. Lobar arteries (n=13) or veins (n=12) were cannulated and perfluoroctyl bromide instilled. Small arteries (0.033 to 0.34 mm Do) and veins (0.024 to 0.33 mm Do) were imaged by planar X-ray at static pressures ranging from 21 to 3 mmHg in 3 mmHg increments. The slope of the pressure/diameter curve was estimated by linear regression (0 = Do + ~P ) for 4·8 arteries or veins per lobe. The linear relationship of all ~ vs their respective Do was plotted (0/00 = 1 + oP) to estimate distensibility. RESULTS: In small arteries, a determined by linear regression was 1.5 ± 0.1% per mmHg as previously described in larger arteries. a estimated in the same way in small veins was significantly lower at 0.9 ± 0.1% per mmHg (p \u3c 0.05). However, the X-ray images suggested that venous diameter increased more at lower than higher pressures. a estimated over the 3-9 mmHg pressure range was 1.4 ± 0.23% per mmHg. while over the 12-21 mmHg pressure range ~ was significantly lower at 0.9% ± 0.13%. CONCLUSIONS: Distensibility of the entire arterial tree over a wide range of pressures seems well described by a single, diameter independent parameter. In contrast, distensibility of small veins appears to be higher at low versus high pressures. Future studies must further examine distensibility of large and small veins at various pressures and relate the findings to pulmonary vascular hemodynamics

Temperature and Performance Inhomogeneities in PEM Electrolysis Stacks with Industrial Scale Cells

In this work temperature inhomogeneities and their influence on PEMWE performance of industrial-scale stacks are investigated. Three temperature differences are examined: (i) between the inlet and outlet, (ii) in-between the cells of a stack, (iii) between the cell’s solid materials and the fluids. A validated stack model for temperature and performance is presented which is used to quantify the above-mentioned temperature fields and their influences on current density distribution and cell voltages. For a chosen scenario, with current densities of 2.0 A cm−2, fluid inlet temperatures of 60 °C and flow-rates of 0.15 kg s−1m−2, peak temperature differences amount to 8.2 K along-the-channel. This relates to inhomogeneities of current density of up to 10% inside a cell and deviations of cell voltage of 9 mV in-between cells in the center of the stack and outer cells. For higher current densities these differences increase further. More homogeneous temperatures allow operation at elevated average temperatures without exceeding temperature limitations and reduce the spread of degradation mechanisms. Hence, homogenous profiles lead to a more hole-some utilization of electrolysis stacks. Therefore, the ability to homogenize via alternative operation such as higher flow-rate, higher pressure and altered routing of fluid-flow is analyzed

Experimental Demonstration of Squeezed State Quantum Averaging

We propose and experimentally demonstrate a universal quantum averaging process implementing the harmonic mean of quadrature variances. The harmonic mean protocol can be used to efficiently stabilize a set of fragile squeezed light sources with statistically fluctuating noise levels. The averaged variances are prepared probabilistically by means of linear optical interference and measurement induced conditioning. We verify that the implemented harmonic mean outperforms the standard arithmetic mean strategy. The effect of quantum averaging is experimentally tested both for uncorrelated and partially correlated noise sources with sub-Poissonian shot noise or super-Poissonian shot noise characteristics.Comment: 4 pages, 5 figure

Ultra-cold atoms in an optical cavity: two-mode laser locking to the cavity avoiding radiation pressure

The combination of ultra-cold atomic clouds with the light fields of optical cavities provides a powerful model system for the development of new types of laser cooling and for studying cooperative phenomena. These experiments critically depend on the precise tuning of an incident pump laser with respect to a cavity resonance. Here, we present a simple and reliable experimental tuning scheme based on a two-mode laser spectrometer. The scheme uses a first laser for probing higher-order transversal modes of the cavity having an intensity minimum near the cavity's optical axis, where the atoms are confined by a magnetic trap. In this way the cavity resonance is observed without exposing the atoms to unwanted radiation pressure. A second laser, which is phase-locked to the first one and tuned close to a fundamental cavity mode drives the coherent atom-field dynamics.Comment: 7 pages, 7 figure

Near-field imaging of optical antenna modes in the mid-infrared

Optical antennas can enhance the coupling between free-space propagating light and the localized excitation of nanoscopic light emitters or receivers, thus forming the basis of many nanophotonic applications. Their functionality relies on an understanding of the relationship between the geometric parameters and the resulting near-field antenna modes. Using scattering-type scanning near-field optical microscopy (s-SNOM) with interferometric homodyne detection, we investigate the resonances of linear Au wire antennas designed for the mid-IR by probing specific vector near-field components. A simple effective wavelength scaling is observed for single wires with lambda(eff) = lambda/(2.0 +/- 0.2), specific to the geometric and material parameters used. The disruption of the coherent current oscillation by introducing a gap gives rise to an effective multipolar mode for the two near-field coupled segments. Using antenna theory and numerical electrodynamics simulations two distinct coupling regimes are considered that scale with gap width or reactive near-field decay length, respectively. The results emphasize the distinct antenna behavior at optical frequencies compared to impedance matched radio frequency (RF) antennas and provide experimental confirmation of theoretically predicted scaling laws at optical frequencies

Altering infrared metamaterial performance through metal resonance damping

Infrared metamaterial design is a rapidly developing field and there are increasing demands for effective optimization and tuning techniques. One approach to tuning is to alter the material properties of the metals making up the resonant metamaterial to purposefully introduce resonance frequency and bandwidth damping. Damping in the infrared portion of the spectrum is unique for metamaterials because the frequency is on the order of the inverse of the relaxation time for most noble metals. Metals with small relaxation times exhibit less resonance frequency damping over a greater portion of the infrared than metals with a longer relaxation time and, subsequently, larger dc conductivity. This leads to the unexpected condition where it is possible to select a metal that simultaneously increases a metamaterial\u27s bandwidth and resonance frequency without altering the geometry of the structure. Starting with the classical microwave equation for thin-film resistors, a practical equivalent-circuit model is developed predicting the sensitivity of infrared metamaterials to complex film impedance. Several full-wave electromagnetic models are developed to validate the resonant-circuit model, and excellent agreement is demonstrated between modeled and measured results

Predictors for failure of supraglottic superimposed high-frequency jet ventilation during endoscopic upper airway surgery in pediatric patients

Airway surgery in pediatric patients is challenging with regard to balancing surgical exposure with ventilation requirements, as during the procedure the airway must be shared between laryngologist and anesthetist. For endoscopic laryngeal surgery, different methods of ventilation are used, among others jet ventilation via a specifically adapted suspension laryngoscope using a dual jet stream(Supraglottic Superimposed High Frequency Jet ventilation, SSHFJV) (1).High BMI and a history of pulmonary pathology proved to be factors contributing to failing of SSHFJV in adult patients (2). However, factors influencing the failure of SSHFJV in pediatric patients have never been described yet