Air Column Research Articles

Measurement and Correction of Atmospheric Effects at Different Altitudes for Remote Sensing of Sun-Induced Fluorescence in Oxygen Absorption Bands

Under sunlight illumination, the shape of the atmospheric oxygen bands [O2-B (687 nm) and O2-A (760 nm)] of the vegetation radiance is modified by chlorophyll fluorescence as a result of the filling-in process. However, for far-range measurements, atmospheric effects also modify this shape. In this paper, measurements of the depth of O2-A and O2-B absorption bands have been performed at different altitudes, from 324 to 3123 m, over different targets, including bare soil and wheat fields. It is observed that bands depth increases significantly with altitude. In the O2-B band, the total magnitude of variation is on the same order of magnitude as the change induced by vegetation, while it is much greater in the O2-A band. Three main factors affect the measurements of band depth: 1) the transmittance of the air column between ground and sensor, 2) the path radiance, and 3) the additional contribution of the ground surface outside the field of view scattered by the atmosphere (adjacency effect). We used the MODerate spectral resolution atmospheric TRANsmittance algorithm (MODTRAN) 4 to compute separately these atmospheric and environmental terms, and we corrected airborne measurements to retrieve ground-level band depths. A study was conducted to assess the sensitivity of the absorption band depth to several atmospheric parameters. The magnitudes of these effects were compared to the band depth variation induced by fluorescence. We identified temperature, air pressure, and aerosols as the most critical parameters. After correction of airborne measurements from atmospheric effects, it is found that the variation of band depth with altitude is greatly reduced. The residual variation, particularly in the case of O2-B band over vegetation, is attributed to an inaccurate assessment of the environment contribution that is scattered by the atmosphere to the sensor. These results show that the MODTRAN 4 is able to simulate oxygen band depth variations at moderate spectral resolution (i.e., 0.5–1 nm) and can be used to compute atmospheric and environmental factors for corrections of airborne measurements of oxygen band profiles. We also showed that an accurate evaluation of the contribution of environment is needed to correct the band depth from atmospheric effects in the O2-B band.

Seasonal emanation of radon at Ghuttu, northwest Himalaya: Differentiation of atmospheric temperature and pressure influences

Continuous monitoring of radon along with meteorological parameters has been carried out in a seismically active area of Garhwal region, northwest Himalaya, within the frame work of earthquake precursory research. Radon measurements are carried out by using a gamma ray detector installed in the air column at a depth of 10m in a 68m deep borehole. The analysis of long time series for 2006–2012 shows strong seasonal variability masked by diurnal and multi-day variations. Isolation of a seasonal cycle by minimising short-time by 31 day running average shows a strong seasonal variation with unambiguous dependence on atmospheric temperature and pressure. The seasonal characteristics of radon concentrations are positively correlated to atmospheric temperature (R=0.95) and negatively correlated to atmospheric pressure (R=−0.82). The temperature and pressure variation in their annual progressions are negatively correlated. The calculations of partial correlation coefficient permit us to conclude that atmospheric temperature plays a dominant role in controlling the variability of radon in borehole, 71% of the variability in radon arises from the variation in atmospheric temperature and about 6% of the variability is contributed by atmospheric pressure. The influence of pressure variations in an annual cycle appears to be a pseudo-effect, resulting from the negative correlation between temperature and pressure variations. Incorporation of these results explains the varying and even contradictory claims regarding the influence of the pressure variability on radon changes in the published literature. Temperature dependence, facilitated by the temperature gradient in the borehole, controls the transportation of radon from the deep interior to the surface.

Synthesis Analysis of One Severe Convection Precipitation Event in Jiangsu Using Ground-Based GPS Technology

Global positioning system (GPS) detection technology has several advantageous characteristics (i.e., all-weather applications, high accuracy, high spatial and temporal resolution, and low cost), and GPS tracking and monitoring techniques for water vapor have developed rapidly in recent years. The GPS-precipitable water vapor (GPS-PWV), obtained through inversion using this technology can reflect the water vapor inflow and outflow in a vertical air column above a certain area in nearly real-time, which is especially important for areas of severe water vapor variation. In this paper, we studied the relationship between GPS-PWV variation and actual precipitation. The specific aim was to identify the underlying physical mechanisms driving the variation and to further strengthen the utility of GPS-PWV in forecasts and warnings of severe convection weather. We concluded that (1) rapid rise in the GPS-PWV in the long-term low-level data predicted the arrival of precipitation and was therefore useful in weather forecasts; (2) the GPS-PWV variation was closely related with the movement of the water vapor transfer belt; (3) the atmosphere showed an unstable energy structure before the GPS-PWV increase; and (4) local motion was strongly related with the development and maintenance of precipitation.

A GCM investigation of dust aerosol impact on the regional climate of North Africa and South/East Asia

The climatic effects of dust aerosols in North Africa and South/East Asia have been investigated using an atmospheric general circulation model, NCEP/GCM/SSiB (Simplified Simple Biosphere Model) and the three-dimensional aerosol data simulated by the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model. GCM simulations show that due to the scattering and absorption of solar radiation by dust particles, surface temperature decreases over both regions, accompanied by a reduced sensible heat flux. However, precipitation responses are different in these two regions. Due to differences in dust location and the associated heating with respect to the rainfall band and circulation, the effect of dust could either enhance or suppress precipitation. Over the North Africa region where dust particles are mainly located to the north of rainfall band, heating of the air column by dust particles forces a stronger ascent motion over dust layers, which induces an anomalous subsidence (or a weakened upward motion) and suppressed cyclonic circulation to its south where precipitation reduces. Furthermore, both humidity and cloud decrease due to the heating in the middle troposphere (semi-direct effect). In South/East Asia, dust particles are located in the upper troposphere over the major rainfall band during the monsoon season, especially Southwest India and the coastal area of Bay of Bengal. Heating of the air column increases upward motion and strengthens cyclonic circulation. Humidity also increases due to the draw-in of the low level moist air. Therefore, cloud and precipitation increase over South/East Asia associated with dust effect. During the pre-monsoon season, when dust particles are located to the north of the monsoon rainfall band, the heating effect results in shifting precipitation northward. The heating of air column due to dust particles, not surface cooling, plays the major role in precipitation changes. The anomalous upward motion over dust regions will induce a subsidence to its south and subsequently reduce precipitation over that region. Therefore, the responses of circulation and precipitation to aerosol forcing depend on the relative location of dust aerosols with respect to rainfall band, which may explain the fact that contradictory results exist regarding whether the aerosol effect would enhance or suppress precipitation. The dust induced change in precipitation is actually more of redistribution rather than the simple action of increase or decrease.

Axial vibrations of brass wind instrument bells and their acoustical influence: Theory and simulations.

Previous work has demonstrated that structural vibrations of brass wind instruments can audibly affect the radiated sound. Furthermore, these broadband effects are not explainable by assuming perfect coincidence of the frequency of elliptical structural modes with air column resonances. In this work a mechanism is proposed that has the potential to explain the broadband influences of structural vibrations on acoustical characteristics such as input impedance, transfer function, and radiated sound. The proposed mechanism involves the coupling of axial bell vibrations to the internal air column. The acoustical effects of such axial bell vibrations have been studied by extending an existing transmission line model to include the effects of a parasitic flow into vibrating walls, as well as distributed sound pressure sources due to periodic volume fluctuations in a duct with oscillating boundaries. The magnitude of these influences in typical trumpet bells, as well as in a complete instrument with an unbraced loop, has been studied theoretically. The model results in predictions of input impedance and acoustical transfer function differences that are approximately 1 dB for straight instruments and significantly higher when coiled tubes are involved or when very thin brass is used.

Alteration in cervical spine mechanics in obstructive sleep apnea syndrome patients

BackgroundObstructive sleep apnea syndrome (OSAS) is a multi-factorial disease with many identified risk factors and mechanisms. Little research exists on cervical spine mechanics as a risk factor for OSAS. ObjectivesThis study aimed to explore the association and predictive value of alterations in cervical spine mechanics with the severity and positional dependency in patients with OSAS. MethodsAfter patient consent and IRB approval, 36 consecutively admitted adult patients (68.1% were males), aged 46years, who underwent clinical evaluation and standard polysomnography were included in this cross-sectional study. Severity scores were estimated from a full night polysomnography sleep study (apnea hypopnea index (AHI), respiratory disturbance index (RDI), desaturation index, overall severity score, snoring index and episodes). Positional dependency for all severity scores was performed. Cervical spine X-rays (PA and lateral) were performed to measure the atlas angle (relative to the horizontal plane) and Cobb angle (a standard measurement for lordosis), the pre-vertebral soft tissue and pharyngeal air column diameter were measured. ResultsMedian BMI (32.63) and sleep apnea indices were high with severe AHI (>30). Positional dependency (63.9%) was significant for RDI. Both the Cobb and atlas angles showed a significantly negative correlation with severity indices and positional dependency. The Cobb angle of lordosis (but not the atlas angle) was a significant negative predictor for all OSAS severity, snoring index and positional dependency. ConclusionIn OSAS patients, there was a significant association between alterations in cervical spine mechanics, severity and positional dependency. Cervical lordosis, but not the atlas angle, was a significant negative predictor of severity and positional dependency. Further studies are needed to validate these results and to study the effect of improving spinal curvature and angular rotation on severity and positional dependency in OSAS patients.

Ectopic internal carotid artery causing oropharyngeal obstruction

An aberrant internal carotid artery (ICA) in the oropharynx is a rare congenital finding. Unless the diagnosis is made before neck or tonsil surgery, massive hemorrhage and even death may result from injury to the vessel. Therefore, knowledge of the presence of aberrant ICAs may be important. We report a rare congenital anomaly of ICAs. Multidetector computed tomography (MDCT) angiography demonstrated an ectopic course of the bilateral ICAs at the level of the oropharynx. It showed compression to the oropharyngeal air column by the left aberrant ICA. A 35-year-old man was referred to our radiology department with the complaints of cervical bolus sensation and intermittent dysphagia for 6 months. He had no history of systemic arterial hypertension or other significant medical problems. Oral examination revealed a pulsatile protrusion through the left posterolateral wall of the oropharynx. In contrast-enhanced MDCT of the neck, a multiplanar reconstruction image at the coronal plane (A) demonstrated an ectopic course of the bilateral ICAs at the level of the oropharynx. Three-dimensional volume-rendered air-specific MDCT was used to show the relationship between the oropharyngeal air column and the ectopic ICA. We have shown that the left-sided aberrant ICA was the cause of severe compression to the oropharyngeal airway (B, arrow). The three-dimensional MDCT image (Cover) also clearly revealed the ectopic course of the bilateral ICAs. Congenitally ectopic position of the ICA is a rare variation and is frequently asymptomatic. The anatomic course of the ICA is normally straight. Incomplete straightening enables the embryonic angulation to persist, resulting in a congenitally tortuous ICA. MDCT angiography can accurately detect the course, caliber, and margin of the ICAs. Showing the presence of an aberrant ICA plays an important role in avoidance of an accidental injury to the vessel during surgery. On the other hand, the retropharyngeal ICA requires no surgical intervention. However, it should be clearly documented in the patient’s medical record.

Five‐day waves in polar stratosphere and mesosphere temperature and mesospheric ice water measured by SOFIE/AIM

AbstractThe temperature and column ice water content (IWC) of polar mesospheric clouds (PMCs) have been simultaneously measured by the Solar Occultation for Ice Experiment (SOFIE) on board NASA's Aeronomy of Ice in the Mesosphere satellite since April 2007. The 8 year (2007–2014) data of the temperature and IWC are used to extract the 5 day planetary waves (PWs) with zonal wave numbers ranging from −1 to −3 (eastward propagating mode, E1–E3), 0 (stationary mode, W0), and 1 to 3 (westward propagating mode, W1–W3) in the polar stratosphere and mesosphere. The 5 day PWs in temperature are stronger in the polar winter stratosphere and mesosphere and exhibit substantial interhemispheric asymmetry. The date‐height distributions of the 5 day waves coincide with those of the eastward jet in each hemisphere. This indicates that the 5 day PWs might be generated from barotropic/baroclinic instability in the polar stratosphere. The relative strengths of 5 day PWs decrease with increasing wave numbers. The E1 (W1) 5 day PW is stronger than any other mode in the winter stratosphere and lower mesosphere (summer upper mesosphere). SOFIE temperature and IWC data are derived from simultaneous measurements in the same air column and thus provide a good opportunity to study the phase relationship between the 5 day PWs in temperature and IWC. Our analyses show that the phase shifts of W1 5 day PW in temperature relative to that in IWC have a mean of −2.0 h (0.3 h) with a standard deviation of 3.8 h (4.2 h) in the northern (southern) polar region. This indicates that the formation of the W1 5 day PW in PMCs is controlled mainly by the W1 5 day PW in temperature and influenced by other factors and is consistent with previous studies.

A negative phase shift of the winter AO/NAO due to the recent Arctic sea‐ice reduction in late autumn

AbstractThis paper examines the possible linkage between the recent reduction in Arctic sea‐ice extent and the wintertime Arctic Oscillation (AO)/North Atlantic Oscillation (NAO). Observational analyses using the ERA interim reanalysis and merged Hadley/Optimum Interpolation Sea Surface Temperature data reveal that a reduced (increased) sea‐ice area in November leads to more negative (positive) phases of the AO and NAO in early and late winter, respectively. We simulate the atmospheric response to observed sea‐ice anomalies using a high‐top atmospheric general circulation model (AGCM for Earth Simulator, AFES version 4.1). The results from the simulation reveal that the recent Arctic sea‐ice reduction results in cold winters in mid‐latitude continental regions, which are linked to an anomalous circulation pattern similar to the negative phase of AO/NAO with an increased frequency of large negative AO events by a factor of over two. Associated with this negative AO/NAO phase, cold air advection from the Arctic to the mid‐latitudes increases. We found that the stationary Rossby wave response to the sea‐ice reduction in the Barents Sea region induces this anomalous circulation. We also found a positive feedback mechanism resulting from the anomalous meridional circulation that cools the mid‐latitudes and warms the Arctic, which adds an extra heating to the Arctic air column equivalent to about 60% of the direct surface heat release from the sea‐ice reduction. The results from this high‐top model experiment also suggested a critical role of the stratosphere in deepening the tropospheric annular mode and modulation of the NAO in mid to late winter through stratosphere‐troposphere coupling.

Demonstration of nonlinear mode coupling in woodwind-like air columns: Recollections from the laboratory of A. H. Benade

Self sustained oscillations in woodwinds are generated by the player's blowing pressure, through the interaction of the standing wave in the air column, the dynamic motion of the reed and the air flow through the reed. In properly designed instruments, the oscillation begins at a threshold blowing pressure near the frequency of an air column resonance. With increased blowing pressure, the amplitude grows and the flow nonlinearity generates harmonics of the playing frequency. The nonlinearity couples the steady state components of the tone. The coupling dictates behaviors that cannot be explained by a linear model. When A. H. Benade came to understand this in the early 1960s, he developed a “tacet horn” whose unplayable behavior could only be explained by the nonlinear theory [Benade and Gans, Ann. N.Y. Acad. Sci. 155, 247–263 (1968)]. Throughout his life, Benade used other pathological air columns for research and pedagogy. This paper will demonstrate two of Benade’s concepts with air columns that are simple to build. One is a clarinet-like tube that can play softly near threshold, but cannot be played louder. The other is a conical tube that plays only at high amplitude.

Air columns for demonstration of upstream/downstream symmetry in reed wind instruments

The acoustics of a reed wind instrument such as a clarinet or oboe, and including the lip-reed instruments such as the trumpet, are classically described by the input impedance of the instrument air column and the dynamical flow control characteristics of the reed valve. The behavior of the system is largely dependent on the resonances of the instrument air column. A fuller explanation however includes both the downstream (usually the instrument) and the upstream (usually the player's wind way) input impedances in symmetry. To demonstrate this, a clarinet-like instrument with no resonance peaks can be played using the resonances of the player's wind way. Another demonstration uses a resonant tube for the upstream air column, with the playing frequency or fundamental based upon a resonance of this upstream tube. The downstream air column has a resonance whose frequency and damping can be set independently of that other resonance. This allows exploration of the effect of a resonance at a harmonic of the playing frequency.

Dynamical analysis and visualization of tornadoes time series.

In this paper we analyze the behavior of tornado time-series in the U.S. from the perspective of dynamical systems. A tornado is a violently rotating column of air extending from a cumulonimbus cloud down to the ground. Such phenomena reveal features that are well described by power law functions and unveil characteristics found in systems with long range memory effects. Tornado time series are viewed as the output of a complex system and are interpreted as a manifestation of its dynamics. Tornadoes are modeled as sequences of Dirac impulses with amplitude proportional to the events size. First, a collection of time series involving 64 years is analyzed in the frequency domain by means of the Fourier transform. The amplitude spectra are approximated by power law functions and their parameters are read as an underlying signature of the system dynamics. Second, it is adopted the concept of circular time and the collective behavior of tornadoes analyzed. Clustering techniques are then adopted to identify and visualize the emerging patterns.

“Wet suction technique (WEST)”: a novel way to enhance the quality of EUS-FNA aspirate. Results of a prospective, single-blind, randomized, controlled trial using a 22-gauge needle for EUS-FNA of solid lesions

Contemporary EUS-guided FNA techniques involve the use of a needle, with an air column within the lumen, with or without suction. We describe a novel technique with an aim to improve the quality of the aspirate. To compare a novel "wet suction" technique (WEST) with the conventional FNA technique (CFNAT) of EUS-guided FNA using a 22-gauge FNA needle. Prospective, single-blind, and randomized trial. Two large tertiary-care hospitals. All consecutive adult patients presenting for EUS with possible FNA of solid lesions were offered the chance to participate in the study. All lesions were sampled with the same needle by using alternating techniques. Patients were randomized to the WEST versus the CFNAT for the first pass. If the first pass was made with the WEST, the second pass was made with the CFNAT, and subsequent passes were made in an alternating manner by using the same sequence. All FNAs were performed using 22-gauge needles. Specimen adequacy, cellularity, and blood contamination of EUS-guided FNA aspirates graded on a predefined scale. The WEST yielded significantly higher cellularity in a cell block compared with the CFNAT, with a mean cellularity score of 1.82±0.76 versus 1.45±0.768 (P<.0003). The WEST cell block resulted in a significantly better specimen adequacy of 85.5% versus 75.2% (P<.035). There was no difference in the amount of blood contamination between the 2 techniques. Lack of cross check and grading by a second cytopathologist. The novel WEST resulted in significantly better cellularity and specimen adequacy in cell blocks of EUS-guided FNA aspirate of solid lesions than the CFNAT.

A new relationship between grain size and fall (settling) velocity in air

The fall velocity of natural sand grains is a fundamental attribute of sediment transport in fluid environments where particles may become partially or fully suspended. Several formulae have been proposed to calculate the fall velocity of particles in air, but there is considerable uncertainty about which is the most accurate or appropriate for a given set of environmental conditions. Five experiments that reported observations of fall velocity of different types of particles in air are described, evaluated, and compared. The experiment data were quality-controlled using four criteria: (1) particles had to have sufficient drop heights to attain their terminal fall velocity; (2) particles had to be in the range of sand sizes; (3) data identified as being problematic by the original authors were removed; and (4) particles comprise natural, irregular shaped sediments. The quality-controlled data were aggregated and analyzed using linear regression to obtain a relationship between grain size ( d, in mm) and fall velocity ( w0, in ms-1): [Formula: see text]. This is a statistically strong relationship with a coefficient of determination of 0.89 ( p &lt; 0.001). This relationship can be regarded as a universal fall velocity model for natural, sand-sized particles falling through a static column of air. In terms of predictive analyses, our heuristic method outperforms alternative formulae and yields a better fit to the experimental data over the full range of sand sizes.

Numerical modeling of power take-off damping in an Oscillating Water Column device

An Oscillating Water Column (OWC) is a wave energy converter consisting of a partially submerged chamber with an air column over the water column. The work done by the air column under excitation by the incident waves is used to generate electrical energy through a power take-off (PTO) device. The air column is under pressure due to the damping from the PTO device and this pressure is essential for the extraction of wave energy using the OWC. The relationship between the PTO damping and the hydrodynamic efficiency of the OWC provides more insight into the wave energy extraction using an OWC.In this paper, two-dimensional Computational Fluid Dynamics (CFD) simulations are used to investigate the response of the OWC under different values of damping from the PTO device. The PTO damping on the chamber is represented using a linear pressure drop law with the permeability coefficient derived from Darcy’s equation for flow through porous media. The model is validated by comparing the numerical results to experimental data. The influence of the PTO damping on the chamber pressure, the free surface motion, the velocity of the vertical motion of the free surface and the hydrodynamic efficiency of the OWC is studied. The hydrodynamic efficiency is calculated as the ratio of the power delivered at the vent of the OWC to the incident wave power. It is found that the PTO damping needed to attain the maximum OWC hydrodynamic efficiency increases with increasing incident wavelength. The formation of stagnation zones in the water due to high velocities for lower values of PTO damping is found to reduce the hydrodynamic efficiency.

Vertical Profiles and Chemical Properties of Aerosol Particles upon Ny-Ålesund (Svalbard Islands)

Size-segregated particle samples were collected in the Arctic (Ny-Ålesund, Svalbard) in April 2011 both at ground level and in the free atmosphere exploiting a tethered balloon equipped also with an optical particle counter (OPC) and meteorological sensors. Individual particle properties were investigated by scanning electron microscopy coupled with energy dispersive microanalysis (SEM-EDS). Results of the SEM-EDS were integrated with particle size and optical measurements of the aerosols properties at ground level and along the vertical profiles. Detailed analysis of two case studies reveals significant differences in composition despite the similar structure (layering) and the comparable texture (grain size distribution) of particles in the air column. Differences in the mineral chemistry of samples point at both local (plutonic/metamorphic complexes in Svalbard) and remote (basic/ultrabasic magmatic complexes in Greenland and/or Iceland) geological source regions for dust. Differences in the particle size and shape are put into relationship with the mechanism of particle formation, that is, primary (well sorted, small) or secondary (idiomorphic, fine to coarse grained) origin for chloride and sulfate crystals and transport/settling for soil (silicate, carbonate and metal oxide) particles. The influence of size, shape, and mixing state of particles on ice nucleation and radiative properties is also discussed.

Cuff leak test and laryngeal survey for predicting post-extubation stridor.

Background and Aims:Evidence for the predictive value of the cuff leak test (CLT) for post-extubation stridor (PES) is conflicting. We evaluated the association and accuracy of CLT alone or combined with other laryngeal parameters with PES.Methods:Fifty-one mechanically ventilated adult patients in a medical-surgical intensive care unit were tested prior to extubation using; CLT, laryngeal ultrasound and indirect laryngoscopy. Biometric, laryngeal and endotracheal tube (ETT) parameters were recorded.Results:PES incidence was 4%. CLT demonstrated ‘no leak’ in 20% of patients. Laryngeal oedema was present in 10% of the patients on indirect laryngoscopy, and 71% of the patients had a Grades 1-3 indirect laryngoscopic view. Mean air column width on laryngeal ultrasound was 0.66 ± 0.15 cm (cuff deflated), mean ratio of ETT to laryngeal diameter was 0.48 ± 0.07, and the calculated CLT and laryngeal survey composite was 0.86 ± 1.25 (range 0-5). CLT and the CLT and Laryngeal survey composite measure were not associated with or predict PES. Age, sex, peri-extubation steroid use, intubation duration and body mass index were not associated with PES.Conclusion:Even including ultrasonographic and indirect laryngoscopic examination of the airway, no single aspect of the CLT or combination with laryngeal parameters accurately predicts PES.

Reappraisal of Pneumoperitoneum After Percutaneous Endoscopic Gastrostomy.

Background/AimsPneumoperitoneum is recognized as a benign and self-limiting finding after the insertion of a percutaneous endoscopic gastrostomy (PEG) tube, while complicated pneumoperitoneum is rarely reported. The aim of this study was to reappraise pneumoperitoneum following PEG.MethodsWe retrospectively reviewed 193 patients who underwent PEG from May 2008 to May 2014. All patients had a follow-up upright chest or simple abdominal radiograph after PEG. Pneumoperitoneum was quantified by measuring the height of the air column under the diaphragm and graded as small (<2 cm), moderate (2-4 cm), or large (>4 cm). Clinically significant signs were defined as fever, abdominal tenderness or leukocytosis occurring after PEG insertion.ResultsOf the 193 study patients, 9 (4.6%) had a pneumoperitoneum visualized by radiographic imaging, graded as small in 5 patients, moderate in 2 patients and large in 2 patients. Clinically significant signs were observed in 5 (55.5%) patients with fever reported in 4 patients, abdominal tenderness in 4 patients and leukocytosis in 4 patients. The time to resolution of free air was 2-18 days. Two patients (22.2%) with moderate or large pneumoperitoneum after PEG died from either pneumonia or septic shock.ConclusionsThe clinical course of pneumoperitoneum after PEG is not always benign and self-limiting. These findings suggest that clinicians should not neglect a moderate or large pneumoperitoneum, particularly in patients who have an altered mental status or received antibiotics, since peritoneal irritation cannot be observed under these circumstances.

Laryngeal air column width ratio in predicting post extubation stridor.

Aim:Correlation of upper air column width ratio in postextubation stridor patients.Materials and Methods:A prospective observational study was conducted in a tertiary hospital between January and December 2013. Patients who were admitted in Intensive Care Unit and intubated for >24 h were included (72 patients). The upper airway air column width ratio (air column width before extubation/air column width after intubation) was calculated and compared in patient with or without postextubation stridor.Results:The incidence of stridor was 6.9% (5/72). The duration of mechanical ventilation was 5.60 ± 1.14 days and 3.91 ± 1.45 days in stridor and nonstridor group respectively. In all 5 patients who had stridor, the upper airway air column width ratio was 0.8 or less.Conclusion:Air column width ratio of 0.8 or less may be helpful in predicting postextubation stridor, which should be confirmed by large observational studies.

Interannual variability of the spring atmospheric heat source over the Tibetan Plateau forced by the North Atlantic SSTA

Data analysis indicates that the interannual variability of the spring atmospheric heat source over the Tibetan Plateau (TP) depends largely on the intensity of the overlying subtropical westerly jet (WJ), which is closely related to the early spring (February–March–April) sea surface temperature anomaly (SSTA) tripole pattern over the North Atlantic, i.e., the SSTA tripole pattern with a warm core to the southeast of Newfoundland and two cold cores to the south of Iceland and southeast of Bermuda, respectively. Such an SSTA pattern can be regarded as a response to the atmospheric forcing of the preceding January–February–March North Atlantic Oscillation. Numerical experiment results from both linear baroclinic model with an idealized diabatic heating profile and an atmospheric general circulation model with prescribed SSTA forcing demonstrate that the warm core alone of the tripole pattern can stimulate a steady downstream Rossby wave train, which further intensifies the spring WJ over the TP. As a result, a positive anomaly of surface sensible heating occurs over most parts of the TP, whereas the precipitation and corresponding latent heating is characterized by a seesaw pattern with a positive/negative anomaly over the northern/southern TP. Meanwhile, the air column radiation cooling effect is enhanced to a certain degree over the plateau. Further analysis suggests that the early spring SSTA over the North Atlantic may exert a seasonal-lagged impact upon the East Asian summer monsoon by modulating the thermal forcing over the TP.