107,538 research outputs found
Data "Nasal and tracheobronchial nitric oxide production and its influence on oxygenation in horses undergoing intravenous anaesthesia"
No full textBackground: In many species a major part of physiological nitric oxide (NO) production takes place in the nasopharynx. Inhaled NO acts as a pulmonary vasodilator and regulates lung perfusion and endotracheal intubation bypasses the nasopharynx.
Objective: To investigate the effect of endotracheal intubation on nasal and tracheal NO concentrations, gas exchange and oxygenation in horses undergoing general anaesthesia.
Study design: Prospective, randomized, experimental cross-over study.
Methods: Six horses were randomly assigned to “intubated” (INT) and “non-intubated” (nINT) treatment groups. Horses were premedicated with dexmedetomidine (5 µg/kg IV). Anaesthesia was induced with 2.5 mg/kg ketamine and 0.05 mg/kg diazepam IV and was maintained by triple-drip (100 mg/kg/h guaifenesin, 4 mg/kg/h ketamine, 7 µg/kg/h dexmedetomidine). The horses were spontaneously breathing room air. Heart rate, cardiac output, arterial blood pressure, pulmonary arterial blood pressures and respiratory rate were recorded during a 100-minute anaesthesia period. Arterial, venous and mixed venous blood samples were taken every ten minutes and analysed for partial pressure of oxygen (PO2) and carbon dioxide (PCO2), oxygen saturation and haemoglobin content. Standard oxygenation indices were calculated. Nasal and tracheal NO concentration was determined by chemiluminescence.
Results: Cardiovascular variables, respiratory rate, PO2, PCO2, oxygen saturation, haemoglobin content, CaO2, O2ER, P(a-ET)CO2 and Qs/Qt did not differ significantly between the two treatment groups. The P(A-a)O2 was significantly higher in INT (6.1 ± 0.3 kPa) compared to nINT (4.9 ± 0.1 kPa) (p = 0.045), respectively. The nasal (8.0 ± 6.2 ppb) and tracheal (13.0 ± 6.3 ppb) NO concentration differed significantly in INT (p = 0.036), but not in nINT (nasal: 16.9 ± 9.0 ppb; tracheal: 18.5 ± 9.5 ppb) (p = 0.215).
Conclusion: Endotracheal intubation reduces the nasal and tracheal NO concentration. The influence on pulmonary gas exchange and oxygenation is neglectable in horses breathing room air
Individual core images of ODP Site 154-925, 154-926, 154-927, 154-928, and 154-929
No full textThese files contain individual core images generated from core box photos using the Code for Ocean Drilling Data (CODD) software set. There are PNG images with mcd depth scales attached for use in graphics programs as well as scaled Igor binary images for use with CODD.
MCD depths are from the offsets included as supplements to: Wilkens, R. H. , T. Westerhold, A. J. Drury, M. Lyle, T. Gorgas, and J. Tian, Revisiting the Ceara Rise, equatorial Atlantic Ocean: isotope stratigraphy of ODP Leg 154, submitted to: Climate of the Past, Jan 2017.
The offsets and splice intervals have been changed from the originals published after the cruise.
The png files are all saved at the same scale and if displayed with the same scaling will all exhibit the same depth scale and core width
Plan of the City of London Ontario, A.D. 1871
No full textPlan of the city of London Ontario, A.D. 1871. Designed by H.A. Wilkens. Original map published 1871. Facsimile of map imprinted on parchment; Facsimile publication unknown.
See notes for story.https://ir.lib.uwo.ca/mdc-London-maps/1020/thumbnail.jp
Sandstone Pore Aspect Ratio Spectra from Direct Observations and Velocity Inversion
No full textMeasurements of pore shapes from Scanning Electron Microscope (SEM) images
for three sandstone samples (the Navajo Sandstone, the Weber Sandstone, and the
Kayenta Sandstone) are compared to the aspect ratio spectra obtained from
inverting laboratory velocity versus pressure data using the method of Cheng and
Toksoz (1979). The results indicate that the inversion method is in very good
agreement with the observations at high aspect ratios ( ex > 0.0 1). At low aspect ratios the agreement is very good for the clean Navajo Sandstone sample, but poor
for the Weber and Kayenta samples which contain clay. The Navajo sample is
composed chiefly of quartz with significant pressure dissolution apparent along grain
contacts resulting in smooth, flat cracks between grains. The Weber and Kayenta
samples have rougher crack surfaces as well as tapered pore edges, indicating that
asperities ,and non-elliptical pore shapes may result in an over estimation of low
aspect ratio cracks by velocity inversion. The presence of degraded feldspars may
also play a role.Phillips Petroleum Fellowshi
Determination of Shear Wave Velocity and Attenuation From Waveforms in Low Velocity Formations
No full textIn boreholes where formation shear velocity is lower than borehole fluid velocity neither refracted shear waves nor pseudo-Rayleigh waves can propagate. When frequency response of the sonde does not extend to low frequencies (e.g. 2 kHz) Stoneley waves are not excited efficiently. In such cases refracted P, leaking modes (PL) and fluid waves become dominant phases on a full waveform acoustic log. The P wave velocity can be determined from the first arrivals. Then, using synthetic microseismograms and a waveform
matching technique, formation shear wave velocity and attenuation can be determined. This method· is demonstrated using data from a well in the Baltimore Canyon Trough area of the Atlantic margin.Massachusetts Institute of Technology. Full Waveform Acoustic Logging Consortiu
Determining Shear Wave Velocities in Soft Marine Sediments
No full textThe inversion technique presented in this volume (Cheng, 1987) that simultaneously
inverts full waveform acoustic logs for shear wave velocity (V[subscript 3]) and compressional wave attenuation (Q[subscript p]) was applied to selected full waveform acoustic logs taken in soft sediments from Deep Sea Drilling Project Site 613.
Besides V[subscript 3] and Q[subscript p], the sensitivity of the inversion to perturbations in the fixed parameters, P-wave velocity (V[subscript p]), fluid velocity (V[[subscript f]), borehole diameter, bulk density (P[subscript b]), and borehole fluid attenuation (Q[subscript f]), were tested. Our study shows that the inversion technique is most sensitive to the estimate of V[subscript p] because the inversion is based
on the P leaky mode energy portion of the spectrum. The Poisson's ratio, however,
which primarily controls the amplitude of the waveforms, is rather stable with different
estimates in V[subscript p]. The inversion technique is less sensitive to small perturbations in borehole diameter, P[subscript b], V[subscript f], and Q[subscript f]
The shear wave velocities inferred from these inversions correlate well with the attendant velocity logs run at Site 613 and the diagenetic changes identified by shipboard stratigraphers. For example, there is an increase in both V[subscript p] and V[subscript 3] at the diagenetic boundary between siliceous nannofossil oozes and porcellanite. This boundary is responsible for a sharp seismic reflector in a USGS. seismic line run nearby. Over the depth interval that we analyzed, from 390.0 to 582.0 meters below sea floor, we determined shear wave velocities ranging from 0.74 to 1.06 km/sec corresponding to compressional wave velocities from 1.70 to 2.20 km/sec.Massachusetts Institute of Technology. Full Waveform Acoustic Logging ConsortiumNational Science Foundation (U.S.) (Grant OCE84-08761)Chevron (Fellowship
Modelling Of Full Waveform Acoustic Logs In Soft Marine Sediments
No full textFull waveform acoustic logs obtained from the Deep Sea Drilling Project (DSDP) were
modelled using synthetic full waveform acoustic logs. These synthetic logs were calculated using the discrete wavenumber method. The model is that of a fluid-filled
borehole with a rigid logging tool in the center. Results from the modelling indicate
that V[subscript p],V[subscript 3] and V[subscript f] along with P wave attenuation (l/Q[subscript 3]) are the primary controls on the full waveform acoustic logs of these soft sediments. S-wave attenuation (l/Q[subscript 3]) does not play a major role because the S-wave velocities (V[subscript 3]) of these fluid-saturated marine
oozes are lower than the borehole fluid velocity (V[subscript f]), thus there is no refracted S-wave or pseudo-Rayleigh wave. However, the formation S-wave velocity does affect the amplitude of the observed P-wave train. Density variations by themselves have almost no discernible effect on the synthetics although in practice a change in density often is concurrent with a change in lithology and formation velocities. Matching the synthetic full waveform acoustic logs to those obtained during Leg 95 of the DSDP was formally done by a least squares linearized iteration inversion procedure. Only the P wavetrain and its associated leaky modes were taken into account. The forward model used in the inversion was a P-wave train generated by the branch cut integral method. Stable
results in V[subscript 3] and Q[subscript p] were obtained. Variations in the velocity and attenuation from the inversion correlates with sedimentary units delineated from conventional logs and lithologic units identified by shipboard stratigraphers for the Baltimore Canyon Trough area. Full waveform logs, in combination with conventional logs, help to identify changes in the physical properties of these sediments as a result of the diagenesis of biogenic silica and calcium carbonate.Massachusetts Institute of Technology. Full Waveform Acoustic Logging ConsortiumChevronTexaco FirmNational Science Foundation (U.S.) (Grant OCE-8408761)Deep Sea Drilling Projec
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Climate, cryosphere and carbon cycle controls on Southeast Atlantic orbital-scale carbonate deposition since the Oligocene (30-0 Ma)
No full textThese are the supplementary datasets for the manuscript: Drury, A.J., Liebrand, D., Westerhold, T., Beddow, H., Hodell, D., Rohlfs, N., Wilkens, R.H., Lourens, L., 'History of South Atlantic carbonate deposition since the Oligocene (30-0 Ma)', in final preparation for submission Climate of the Pas
Serum parameters related to mineral homeostasis and energy metabolism in ewes kept on different dietary magnesium supply during the transition period
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