Impact of right ventricular distensibility on congestive heart failure with preserved left ventricular ejection fraction in the elderly.

PubMed

Harada, Daisuke; Aasanoi, Hidetsugu; Ushijima, Ryuichi; Noto, Takahisa; Takagawa, Junya; Ishise, Hisanari; Inoue, Hiroshi

2018-06-01

To elucidate involvement of age-related impairments of right ventricular (RV) distensibility in the elderly congestive heart failure (CHF), we examined the prevalence of less-distensible right ventricle in patients with preserved left ventricular ejection fraction (LVEF) over a wide range of ages. In 893 patients aged from 40 to 102 years, we simultaneously recorded electrocardiogram, phonocardiogram, and jugular venous pulse wave. Using signal-processing techniques, the prominent 'Y' descent of jugular pulse waveform was detected as a hemodynamic sign of a less-distensible right ventricle. Prevalence of less-distensible right ventricle and elevated RV systolic pressure increased along with aging from the 50s to the 90s in an exponential fashion from 3.3 and 12% up to 33 and 61%, respectively (p < 0.001 for each). This age-dependent deterioration of ventricular distensibility was not observed for the left ventricle. Higher age and higher RV systolic pressure were independently associated with less-distensible right ventricle (Odds ratio, 1.05 per 1 year, p = 0.003; and 1.03 per 1 mmHg, p = 0.026, respectively). The elderly CHF was associated with high prevalence of the less-distensible right ventricle and higher RV systolic pressure, both of which were independent risk factors for CHF (Odds ratio, 5.27, p = 0.001, and 1.08 per 1 mmHg, p < 0.001, respectively). In elderly patients with preserved LVEF, the combination of a less-distensible right ventricle and a high RV systolic pressure seems to be related to developing CHF. The less-distensible right ventricle and elevated RV systolic pressure are closely associated with CHF with preserved LVEF in the elderly patients.

Pathologic aerophagia: a rare cause of chronic abdominal distension

PubMed Central

de Jesus, Lisieux Eyer; Cestari, Ana Beatriz C.S.S.; da Silva, Orli Carvalho; Fernandes, Marcia Antunes; Firme, Livia Honorato

2015-01-01

Objective: To describe an adolescent with pathologic aerophagia, a rare condition caused by excessive and inappropriate swallowing of air and to review its treatment and differential diagnoses. Case description: An 11-year-old mentally impaired blind girl presenting serious behavior problems and severe developmental delay with abdominal distension from the last 8 months. Her past history included a Nissen fundoplication. Abdominal CT and abdominal radiographs showed diffuse gas distension of the small bowel and colon. Hirschsprung's disease was excluded. The distention was minimal at the moment the child awoke and maximal at evening, and persisted after control of constipation. Audible repetitive and frequent movements of air swallowing were observed. The diagnosis of pathologic aerophagia associated to obsessive-compulsive disorder and developmental delay was made, but pharmacological treatment was unsuccessful. The patient was submitted to an endoscopic gastrostomy, permanently opened and elevated relative to the stomach. The distention was resolved, while maintaining oral nutrition. Comments: Pathologic aerophagia is a rare self-limiting condition in normal children exposed to high levels of stress and may be a persisting problem in children with psychiatric or neurologic disease. In this last group, the disease may cause serious complications. Pharmacological and behavioral treatments are ill-defined. Severe cases may demand surgical strategies, mainly decompressive gastrostomy. PMID:26100594

Abdominothoracic mechanisms of functional abdominal distension and correction by biofeedback.

PubMed

Barba, Elizabeth; Burri, Emanuel; Accarino, Anna; Cisternas, Daniel; Quiroga, Sergi; Monclus, Eva; Navazo, Isabel; Malagelada, Juan-R; Azpiroz, Fernando

2015-04-01

In patients with functional gut disorders, abdominal distension has been associated with descent of the diaphragm and protrusion of the anterior abdominal wall. We investigated mechanisms of abdominal distension in these patients. We performed a prospective study of 45 patients (42 women, 24-71 years old) with functional intestinal disorders (27 with irritable bowel syndrome with constipation, 15 with functional bloating, and 3 with irritable bowel syndrome with alternating bowel habits) and discrete episodes of visible abdominal distension. Subjects were assessed by abdominothoracic computed tomography (n = 39) and electromyography (EMG) of the abdominothoracic wall (n = 32) during basal conditions (without abdominal distension) and during episodes of severe abdominal distension. Fifteen patients received a median of 2 sessions (range, 1-3 sessions) of EMG-guided, respiratory-targeted biofeedback treatment; 11 received 1 control session before treatment. Episodes of abdominal distension were associated with diaphragm contraction (19% ± 3% increase in EMG score and 12 ± 2 mm descent; P < .001 vs basal values) and intercostal contraction (14% ± 3% increase in EMG scores and 6 ± 1 mm increase in thoracic antero-posterior diameter; P < .001 vs basal values). They were also associated with increases in lung volume (501 ± 93 mL; P < .001 vs basal value) and anterior abdominal wall protrusion (32 ± 3 mm increase in girth; P < .001 vs basal). Biofeedback treatment, but not control sessions, reduced the activity of the intercostal muscles (by 19% ± 2%) and the diaphragm (by 18% ± 4%), activated the internal oblique muscles (by 52% ± 13%), and reduced girth (by 25 ± 3 mm) (P ≤ .009 vs pretreatment for all). In patients with functional gut disorders, abdominal distension is a behavioral response that involves activity of the abdominothoracic wall. This distension can be reduced with EMG-guided, respiratory-targeted biofeedback therapy. Copyright © 2015 AGA

Perineal Distensibility Using Epi-no in Twin Pregnancies: Comparative Study with Singleton Pregnancies

PubMed Central

Kubotani, Juliana Sayuri; Moron, Antonio Fernandes; Zanetti, Miriam Raquel Diniz; Soares, Vanessa Cardoso Marques; Elito Júnior, Julio

2014-01-01

The aims of this study were to compare perineal distensibility between women with twin and singleton pregnancies and to correlate these women's perineal distensibility with anthropometric data. This prospective cross-sectional case-control study was conducted among nulliparous women, of whom 20 were pregnant with twins and 23 with a single fetus. Perineal distensibility was evaluated in the third trimester by means of Epi-no, which was introduced into the vagina and inflated up to the maximum tolerable limit. It was then withdrawn while inflated and its circumference was measured. The unpaired Student's t-test was used to compare perineal distensibility in the two groups and Pearson's correlation coefficient (r) was used to correlate the pregnant women's perineal distensibility with their anthropometric data. There was no difference in perineal distensibility between the twin group (16.51 ± 2.05 cm) and singleton group (16.13 ± 1.67 cm) (P = 0.50). There was a positive correlation between perineal distensibility and abdominal circumference (r = 0.36; P = 0.01). The greater the abdominal circumference was, the greater the perineal distensibility was, regardless of whether the pregnancy was twin or singleton. PMID:25006476

Adhesive capsulitis of the shoulder: the rate of manipulation following distension arthrogram.

PubMed

Ibrahim, T; Rahbi, H; Beiri, A; Jeyapalan, K; Taylor, G J S

2006-11-01

To determine the rate of manipulation under anaesthesia (MUA) following distension arthrogram for adhesive capsulitis of the shoulder. Thirty-nine patients (42 shoulders) between 1998 and 2004 were treated with distension arthrogram for adhesive capsulitis diagnosed by the clinical picture of progressive pain and stiffness. Capsular disruption into the subscapular bursa was demonstrated in 40 of the 42 shoulders (95%). Thirty-seven of 42 (88%) shoulders were painfree following distension arthrogram. 15 of 42 (36%) shoulders underwent MUA following distension arthrogram for stiffness although 10 of these (67%) were painfree. Prior to distension arthrogram, the range of external rotation (ER) was no different between those that had MUA and those that did not (P = 0.36). The improvement in ER was 33% (P = 0.28) in those that had MUA and 50% (P = 0.001) in those that did not. The only complication was a vasovagal episode during the procedure. Distension arthrogram can be used as a therapeutic procedure for achieving symptomatic pain relief in the majority of adhesive capsulitis and decrease the rate of MUA of the shoulder.

Carotid artery distensibility and hormone therapy and menopause: the Los Angeles Atherosclerosis Study.

PubMed

Shufelt, Chrisandra; Elboudwarej, Omeed; Johnson, B Delia; Mehta, Puja; Bittner, Vera; Braunstein, Glenn; Berga, Sarah; Stanczyk, Frank; Dwyer, Kathleen; Merz, C Noel Bairey

2016-02-01

Observational studies have suggested that arterial distensibility decreases during menopause; however, its relationship with hormone therapy use remains controversial. We prospectively studied distensibility and hormone therapy use at different menopause stages. One hundred sixty-one women (aged between 42 and 61 y) without cardiovascular disease underwent carotid artery measurements by ultrasound to calculate distensibility index at baseline and 3 years later. Menopause stage was classified at each visit as premenopausal, perimenopausal, and postmenopausal. Across 3 years of prospective observation, women were classified as remaining premenopausal, remaining postmenopausal, or transitioning (defined as change from premenopausal to perimenopausal, from premenopausal to postmenopausal, from perimenopausal to perimenopausal, or from perimenopausal to postmenopausal). Distensibility declined across time at all menopause stages (P < 0.0001). Compared with postmenopausal women, premenopausal and transitioning/no hormone therapy women had more than twice the decline in distensibility index (P = 0.06 and P = 0.016, respectively), whereas transitioning/hormone therapy women did not differ in distensibility decline (P = 0.28). In a multivariate model, change in systolic blood pressure (P < 0.0001) and change in pulse pressure (P = 0.004) were independent predictors of distensibility index change and served as effect modulators. In an adjusted model, women in the premenopausal and transitioning/no hormone therapy groups had a significantly faster decline in distensibility index (P = 0.002 and P = 0.001, respectively) compared with postmenopausal women, whereas the transitioning/hormone therapy group did not (P = 0.21). These findings confirm that the menopausal transition is associated with reduced vascular compliance. Hormone therapy is associated with better arterial distensibility only during the menopausal transition. Additional prospective studies are needed to confirm

[Pathologic aerophagia: a rare cause of chronic abdominal distension].

PubMed

de Jesus, Lisieux Eyer; Cestari, Ana Beatriz C S S; Filho, Orli Carvalho da Silva; Fernandes, Marcia Antunes; Firme, Livia Honorato

2015-01-01

To describe an adolescent with pathologic aerophagia, a rare condition caused by excessive and inappropriate swallowing of air and to review its treatment and differential diagnoses. An 11 year-old mentally impaired blind girl presenting serious behavior problems and severe developmental delay with abdominal distension from the last 8 months. Her past history included a Nissen fundoplication. Abdominal CT and abdominal radiographs showed diffuse gas distension of the small bowel and colon. Hirschsprung's disease was excluded. The distention was minimal at the moment the child awoke and maximal at evening, and persisted after control of constipation. Audible repetitive and frequent movements of air swallowing were observed. The diagnosis of pathologic aerophagia associated to obsessive compulsive disorder and developmental delay was made, but pharmacological treatment was unsuccessful. The patient was submitted to an endoscopic gastrostomy, permanently opened and elevated relative to the stomach. The distention was resolved, while maintaining oral nutrition Pathologic aerophagia is a rare self-limiting condition in normal children exposed to high levels of stress and may be a persisting problem in children with psychiatric or neurologic disease. In this last group, the disease may cause serious complications. Pharmacological and behavioral treatments are ill-defined. Severe cases may demand surgical strategies, mainly decompressive gastrostomy. Copyright © 2015 Sociedade de Pediatria de São Paulo. Publicado por Elsevier Editora Ltda. All rights reserved.

Pharmacologic evaluation of pressor and visceromotor reflex responses to bladder distension.

PubMed

Su, Xin; Riedel, Erin S; Leon, Lisa A; Laping, Nicholas J

2008-01-01

Several mechanisms that are involved in acute rat bladder nociception were examined. The nociceptive response was measured by analyzing both cardiovascular and visceromotor reflex responses to urinary bladder distension. The contributions of micro-opioid receptor, kappa-opioid receptor, sodium channels, muscarinic receptors, and cyclooxygenase, were explored with morphine, U50,488, mexiletine, oxybutynin, and naproxen, respectively. Female Sprague-Dawley rats were acutely instrumented with jugular venous, carotid arterial, and bladder cannulas. Needle electrodes were placed directly into the abdominal musculature to measure myoelectrical activity subsequent to repeated phasic urinary bladder distension (60 mmHg for 20 sec in 3 min intervals) under 1% isoflurane. Drugs were administered by i.v. bolus injection 2 min prior to distension. The analgesics morphine (ID50 0.69 mg/kg), U50,488 (1.34 mg/kg), and mexiletine (2.60 mg/kg) significantly inhibited the visceromotor reflex response to noxious urinary bladder distension. Oxybutynin also attenuated reflex responses to noxious urinary bladder distension to 41% of the maximal pressor response and 32% of the control visceromotor reflex response (3.01 and 5.05 mg/kg), respectively, indicating a role of muscarinic receptors in bladder nociception. Naproxen did not attenuate the pressor response, but moderately inhibited visceromotor reflex to 45% of control at 30 mg/kg (P < 0.05). Current results using the rat urinary bladder distension model are consistent with previous research demonstrating a role of the analgesics (morphine, U50,488, and mexiletine) in the inhibition of visceral nociceptive transmission. The utility of the reflex responses to urinary bladder distension may provide a method useful to examine mechanisms which target the bladder sensory pathway. (c) 2007 Wiley-Liss, Inc.

Rectal distensibility and symptoms after stapled and Milligan-Morgan operation for hemorrhoids.

PubMed

Corsetti, Maura; De Nardi, Paola; Di Pietro, Salvatore; Passaretti, Sandro; Testoni, Pier Alberto; Staudacher, Carlo

2009-12-01

In a previous uncontrolled study, a reduction of rectal distensibility and volume thresholds for sensations have been related to the occurrence of fecal urgency and/or increased stool frequency after stapled hemorrhoidopexy. The aim of this study was to compare rectal symptoms and sensory-motor function after stapled hemorrhoidopexy and Milligan-Morgan hemorrhoidectomy. The clinical records of 12 (four women) and ten patients (four women) with third- and fourth-degree hemorrhoids, respectively, who underwent stapled hemorrhoidopexy or Milligan-Morgan's hemorrhoidectomy, were evaluated. One week before and 6 months after surgery, rectal motor and sensory response to distension was assessed by an electronic barostat, and bowel and rectal symptoms were recorded by means of a 7-day diary and Bristol Index scale and psychological symptoms with SCL-90 questionnaire. Rectal distensibility and volume thresholds for sensations were significantly lower after surgery (P < 0.02) in the stapled group. Increased stool frequency and/or fecal urgency arose in 41% of patients in the stapled group and associated with altered rectal distensibility. No difference within and between groups could be demonstrated in SCL-90 score. Rectal distensibility and volume thresholds for sensations decrease after stapled hemorrhoidopexy. Altered rectal distensibility was associated with rectal urgency and/or increased stool frequency.

Carotid Artery Distensibility and Hormone Therapy and Menopause: The Los Angeles Atherosclerosis Study (LAAS)

PubMed Central

Shufelt, Chrisandra; Elboudwarej, Omeed; Johnson, B. Delia; Mehta, Puja; Bittner, Vera; Braunstein, Glenn; Berga, Sarah; Stanczyk, Frank; Dwyer, Kathleen; Merz, C. Noel Bairey

2015-01-01

Objective Observational studies suggest that arterial distensibility decreases during menopause; however, the relation to hormone therapy use is controversial. We prospectively studied distensibility and hormone therapy use during different menopause stages. Methods 161 women between 42–61 years of age without cardiovascular disease had carotid artery measurements by ultrasound to calculate the distensibility index at baseline and 3 years later. Menopause stage was classified at each visit as premenopausal, perimenopausal, and postmenopausal. Over 3 years of prospective observation, women were classified as remaining premenopausal, remaining postmenopausal, or transitioning, defined as change from premenopausal-to-perimenopausal, premenopausal-to-postmenopausal, perimenopausal-to-perimenopausal, or perimenopausal-to-postmenopausal. Results Distensibility declined over time in all menopause stages (p<0.0001). Compared to postmenopausal women, premenopausal and transitioning/no hormone therapy women had over twice the decline in distensibility index (p=0.06 and p=0.016, respectively), whereas transitioning/hormone therapy did not differ in distensibility decline (p=0.28). In a multivariate model, change in systolic blood pressure (p<0.0001) and change in pulse pressure (p=0.004) were independent predictors of distensibility index change and served as effect modulators. In the adjusted model, women in the premenopausal and transitioning/no hormone therapy groups had a significantly faster distensibility index decline (p=0.002 and 0.001, respectively) than postmenopausal women, while the transitioning/hormone therapy group did not (p=0.21) Conclusions These findings confirm that menopause transition is associated with reduced vascular compliance. Hormone therapy is associated with better arterial distensibility only during menopause transition. Additional prospective studies are needed to confirm these findings and to determine if hormone therapy use beyond menopause

The effect of esophageal and gastric distension on the crural diaphragm.

PubMed

Shafik, Ahmed; Shafik, Ismail; El Sibai, Olfat; Mostafa, Randa M

2006-02-01

The mechanism of prevention of gastric reflux into the esophagus is not exactly known. The lower esophagus has a barrier function provided by the lower esophageal sphincter. We investigated the hypothesis that the crural diaphragm shares in the barrier function not only mechanically but also actively through a crural-esophageal-gastric reflex action. The study was performed during repair of abdominal ventral and incisional hernias in 20 subjects (11 men, 9 women; age 38.6+/-4.8 years). The electromyographic response of the crural diaphragm to individual balloon distension of esophagus and stomach was recorded by means of a needle electrode inserted into the crural diaphragm and connected to an electromyographic apparatus. The recordings were repeated after separate crural, esophageal, and gastric anesthetization. The crural diaphragm exhibited basal motor unit action potentials, which decreased on esophageal distension (P<0.001) after a mean latency of 17.3+/-2.8 SD ms. The crural diaphragm response to esophageal distension did not occur after the crural diaphragm or esophagus was anesthetized. Gastric distension effected an increase of crural diaphragm electromyographic activity with a mean latency of 18.4+/-4.6 ms; this effect could not be achieved after the crural diaphragm or stomach was anesthetized. The crural diaphragm has a resting tone that relaxes after esophageal distension and contracts after gastric distension. This sphincter-like action of the crural diaphragm appears to be a reflex and is mediated through the esophagocrural inhibitory and gastrocrural excitatory reflexes. The crural diaphragm seems to share actively in the gastroesophageal competence mechanism.

Esophagogastric junction distensibility assessed using the functional lumen imaging probe

PubMed Central

Chen, Joan W; Rubenstein, Joel H

2017-01-01

AIM To assess reference values in the literature for esophageal distensibility and cross-sectional area in healthy and diseased subjects measured by the functional lumen imaging probe (FLIP). METHODS Systematic search and review of articles in Medline and Embase pertaining to the use of FLIP in the esophagus was conducted in accordance with the PRISMA guidelines. Cross-sectional area and distensibility at the esophagogastric junction (EGJ) were abstracted for normal subjects, achalasia, and gastroesophageal reflux disease (GERD) patients, stratified by balloon length and volume of inflation. RESULTS Six achalasia studies (n = 154), 3 GERD (n = 52), and 5 studies including healthy controls (n = 98) were included in the systematic review. Normative data varied widely amongst studies of healthy volunteers. In contrast, studies in achalasia patients uniformly demonstrated low point estimates in distensibility ≤ 1.6 mm2/mmHg prior to treatment that increased to ≥ 3.4 mm2/mmHg following treatment at 40mL bag volume. In GERD patients, distensibility fell to the range of untreated achalasia (≤ 2.85 mm2/mmHg) following fundoplication. CONCLUSION FLIP may be a useful tool in assessment of treatment efficacy in achalasia. The drastic drop in EGJ distensibility after fundoplication suggests that FLIP measurements need to be interpreted in the context of esophageal body motility and highlights the importance of pre-operative screening for dysmotility. Future studies using standardized FLIP protocol and balloon size are needed. PMID:28275309

TENS attenuates response to colon distension in paraplegic and quadriplegic rats.

PubMed

Collins, Heidi L; DiCarlo, Stephen E

2002-10-01

Individuals with spinal cord injuries above thoracic level 6 experience episodic bouts of life-threatening hypertension as part of a condition termed autonomic dysreflexia (AD). The hypertension can be caused by stimulation of the skin, distension of the urinary bladder or colon, and/or muscle spasms. Transcutaneous electrical nerve stimulation (TENS) may reduce the severity of AD because TENS has been used to inhibit second-order neurons in the dorsal horn. Therefore, we tested the hypothesis that TENS attenuates the hemodynamic responses to colon distension. Eleven Wistar rats underwent spinal cord transection between thoracic vertebrae 4 and 5 (paraplegic, n = 6) or between cervical vertebra 7 and thoracic vertebra 1 (quadriplegic, n = 5). After recovery, all rats were instrumented with a radiotelemetry device for recording arterial pressure. Subsequently, the hemodynamic responses to graded colon distension were determined before and during TENS. During TENS the hemodynamic responses to colon distension were significantly attenuated. Thus TENS may be a preventive approach to reduce the severity of AD in paraplegic and quadriplegic individuals.

Distension of the esophagogastric junction augments triggering of transient lower esophageal sphincter relaxation.

PubMed

van Wijk, Michiel P; Blackshaw, L Ashley; Dent, John; Benninga, Marc A; Davidson, Geoffrey P; Omari, Taher I

2011-10-01

Patients with gastroesophageal reflux disease show an increase in esophagogastric junction (EGJ) distensibility and in frequency of transient lower esophageal sphincter relaxations (TLESR) induced by gastric distension. The objective was to study the effect of localized EGJ distension on triggering of TLESR in healthy volunteers. An esophageal manometric catheter incorporating an 8-cm internal balloon adjacent to a sleeve sensor was developed to enable continuous recording of EGJ pressure during distension of the EGJ. Inflation of the balloon doubled the cross-section of the trans-sphincteric portion of the catheter from 5 mm OD (round) to 5 × 11 mm (oval). Ten healthy subjects were included. After catheter placement and a 30-min adaptation period, the EGJ was randomly distended or not, followed by a 45-min baseline recording. Subjects consumed a refluxogenic meal, and recordings were made for 3 h postprandially. A repeat study was performed on another day with EGJ distension status reversed. Additionally, in one subject MRI was performed to establish the exact position of the balloon in the inflated state. The number of TLESR increased during periods of EGJ distension with the effect being greater after a meal [baseline: 2.0(0.0-4.0) vs. 4.0(1.0-11.0), P=0.04; postprandial: 15.5(10.0-33.0) vs. 22.0(17.0-58.0), P=0.007 for undistended and distended, respectively]. EGJ distension augments meal-induced triggering of TLESR in healthy volunteers. Our data suggest the existence of a population of vagal afferents located at sites in/around the EGJ that may influence triggering of TLESR.

Influence of blood flow velocity on arterial distensibility of carotid artery in healthy men.

PubMed

Tomoto, Tsubasa; Maeda, Seiji; Sugawara, Jun

2017-01-01

Decreased distensibility of carotid artery is independently associated with the incidence of cardiovascular and cerebrovascular events. Arterial distensibility is determined by vascular tone. Since shear stress is an important driving force of vasodilatory substances production form endothelial cells, we hypothesized that local basal (i.e., resting) arterial blood flow velocity is associated with regional arterial distensibility. To test this hypothesis, we determined the influence of local blood flow velocity on carotid arterial distensibility in cross-sectional study design. In a total of 73 apparent healthy men (18-64 years), carotid arterial properties, including measures of carotid arterial distensibility and BFV at rest, were evaluated via B-mode and Doppler ultrasound imaging and applanation tonometry system. Carotid arterial peak BFV and the absolute and normalized pulsatile BFV significantly correlated with age (r = -0.453 to -0.600, p < 0.0001), whereas mean and minimum BFV were not influenced by age. Distensibility coefficient of carotid artery correlated with peak BFV (r = 0.305, p < 0.01) and more strongly with pulsatile (i.e., systolic minus end-diastolic) BFV (r = 0.406, p < 0.0001) and the normalized pulsatile BFV by time-averaged velocity (r = 0.591, p < 0.0001). Multi-regression analysis revealed that age (β = -0.57, p < 0.0001) was the primary independent determinant for distensibility coefficient. In addition with this, carotid lumen diameter (β = -0.202, p < 0.01) and the normalized pulsatile BFV (β = 0.237, p < 0.05) were significant independent determinants of distensibility coefficient. Qualitatively similar results (although inverse in direction) were obtained by use of β-stiffness index. These results suggest that greater gradient of blood flow velocity during a cardiac cycle are favorably associated with distensibility of carotid artery.

Stomach distension increases efferent muscle sympathetic nerve activity and blood pressure in healthy humans.

PubMed

Rossi, P; Andriesse, G I; Oey, P L; Wieneke, G H; Roelofs, J M; Akkermans, L M

1998-12-11

Although the enteric nervous system is usually described as a separate and independent entity, animal studies show that gastric distension causes a reflex increase in arterial pressure and a sympathetically mediated increase in heart rate and peripheral vascular resistance. To assess the influence of gastric distension on sympathetic outflow and blood pressure, we recorded muscle sympathetic nerve activity (MSNA) from the peroneal nerve by microneurography in eight healthy volunteers. The stomach was distended by means of a barostat, using a single staircase protocol by which pressure was increased by 2 mmHg every 3 min. Gastric sensory function was assessed at each distension step by using a visual analog scale (VAS) for sensations of fullness, nausea and pain. For comparison, we also performed a cold pressor test. The MSNA increased on barostat-induced gastric distension with an almost concomitant elevation of blood pressure. The increase in both was proportional to the intragastric pressure and both decreased towards initial values after the end of distension. Heart rate increased inconsistently and only at higher distension pressures that were associated with high VAS scores. The opposite was found for the cold pressor test. The results of this study confirm the existence of a functional relationship between gastrointestinal distension and cardiovascular function. Decrease in this gastrovascular response may play a role in postprandial hypotension in the elderly, since the MSNA responses to simulated microgravity decrease with age.

Effect of sympathetic nerves on composition and distensibility of cerebral arterioles in rats.

PubMed Central

Baumbach, G L; Heistad, D D; Siems, J E

1989-01-01

1. The goals of this study were to examine the effects of chronic sympathetic denervation on the mechanics and composition of cerebral arterioles in normotensive Wistar Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). 2. We used an in vivo method to examine the mechanics of pial arterioles in 10- to 12-month-old, anaesthetized WKY and SHRSP that had undergone unilateral removal of the superior cervical ganglion at 1 month of age. Bilateral craniotomies were performed in each rat to expose pial arterioles in the innervated and denervated cerebral hemispheres. Arterioles were deactivated with EDTA. Incremental distensibility and stress-strain relationships were calculated from measurements of pial arteriolar pressure (servo null), diameter and cross-sectional area of the arteriolar wall. Point counting stereology was used to quantify volume density and cross-sectional area of individual components in the arteriolar wall. 3. Chronic sympathetic denervation reduced cross-sectional area of the arteriolar wall by 16 +/- 2% (mean +/- S.E. of mean; P less than 0.05) in WKY and 44 +/- 3% in SHRSP. During maximal dilatation with EDTA, incremental distensibility was reduced and the stress-strain curve was shifted to the left in denervated arterioles of SHRSP, but not WKY. These findings indicate that sympathetic denervation in SHRSP attenuates the development of hypertrophy in pial arterioles and reduces arteriolar distensibility. The ratio of non-distensible (collagen and basement membrane) to distensible (smooth muscle, elastin and endothelium) components was reduced in denervated arterioles in SHRSP, but not WKY. 4. Thus, sympathetic nerves have trophic effects on cerebral arterioles in WKY and, to a greater degree, in SHRSP. Sympathetic nerves also contribute to increases in distensibility of cerebral arterioles in SHRSP, but not WKY. The increase in arteriolar distensibility is accompanied by a disproportionate increase in the more compliant

Ultrasonographic study of mechanosensory properties in human esophagus during mechanical distension

PubMed Central

Larsen, Ejnar; Reddy, Hariprasad; Drewes, Asbjørn Mohr; Arendt-Nielsen, Lars; Gregersen, Hans

2006-01-01

AIM: To study the esophageal geometry and mechanosensation using endoscopic ultrasonography during volume-controlled ramp distensions in the distal esophagus. METHODS: Twelve healthy volunteers underwent distension of a bag. During distension up to moderate pain the sensory intensity was assessed on a visual analogue scale (VAS). The esophageal deformation in terms of multidimensional stretch ratios and strains was calculated at different volumes and VAS levels. Distensions were done before and during administration of the anti-cholinergic drug butylscopolamine. RESULTS: The stimulus-response (volume-VAS) curve did not differ without or with the administration of butylscopolamine. Analysis of stretch ratios demonstrated tensile stretch in circumferential direction, compression in radial direction and a small tensile stretch in longitudinal direction. A strain gradient existed throughout the esophageal wall with the largest circumferential deformation at the mucosal surface. The sensation intensity increased exponentially as function of the strains. CONCLUSION: The method provides information of esophageal deformation gradients that correlate to the sensation intensity. Hence, it can be used to study mechanosensation in the human esophagus. Further studies are needed to determine the exact deformation stimulus for the esophageal mechanoreceptors. PMID:16874864

Crural diaphragm inhibition during esophageal distension correlates with contraction of the esophageal longitudinal muscle in cats.

PubMed

Liu, Jianmin; Puckett, James L; Takeda, Torahiko; Jung, Hwoon-Yong; Mittal, Ravinder K

2005-05-01

Esophageal distension causes simultaneous relaxation of the lower esophageal sphincter (LES) and crural diaphragm. The mechanism of crural diaphragm relaxation during esophageal distension is not well understood. We studied the motion of crural and costal diaphragm along with the motion of the distal esophagus during esophageal distension-induced relaxation of the LES and crural diaphragm. Wire electrodes were surgically implanted into the crural and costal diaphragm in five cats. In two additional cats, radiopaque markers were also sutured into the outer wall of the distal esophagus to monitor esophageal shortening. Under light anesthesia, animals were placed on an X-ray fluoroscope to monitor the motion of the diaphragm and the distal esophagus by tracking the radiopaque markers. Crural and costal diaphragm electromyograms (EMGs) were recorded along with the esophageal, LES, and gastric pressures. A 2-cm balloon placed 5 cm above the LES was used for esophageal distension. Effects of baclofen, a GABA(B) agonist, were also studied. Esophageal distension induced LES relaxation and selective inhibition of the crural diaphragm EMG. The crural diaphragm moved in a craniocaudal direction with expiration and inspiration, respectively. Esophageal distension-induced inhibition of the crural EMG was associated with sustained cranial motion of the crural diaphragm and esophagus. Baclofen blocked distension-induced LES relaxation and crural diaphragm EMG inhibition along with the cranial motion of the crural diaphragm and the distal esophagus. There is a close temporal correlation between esophageal distension-mediated LES relaxation and crural diaphragm inhibition with the sustained cranial motion of the crural diaphragm. Stretch caused by the longitudinal muscle contraction of the esophagus during distension of the esophagus may be important in causing LES relaxation and crural diaphragm inhibition.

Phosphorylation of spinal signaling-regulated kinases by acute uterine cervical distension in rats.

PubMed

Wang, L Z; Liu, X; Wu, W X; Chai, R K; Chang, X Y

2010-01-01

Spinal extracellular signaling-regulated kinase 1 and 2 (ERK 1/2) have been found to contribute to nociceptive processing, but the role of spinal ERK 1/2 in visceral pain related to the uterine cervix, the source of pain during the first stage of labor, is unknown. The aim of this study was to investigate ERK activation (phosphorylation) in spinal dorsal horn neurons after acute uterine cervical distension. Under intraperitoneal anesthesia using chloral hydrate 300 mg/kg, female Sprague-Dawley rats were exposed to a 10-s uterine cervical distension of 25, 50, 75, and 100g or no distension (sham). The electromyographic response in the rectus abdominis muscle and mean arterial blood pressure and heart rate changes to uterine cervical distension were determined. The numbers of phosphorylated-ERK 1/2- immunoreactive (pERK 1/2-IR) dorsal horn neurons in cervical (C5-8), thoracic (T5-8), thoracolumbar (T12-L2) and lumbosacral (L(6)-S(1)) segments were counted using immunohistochemistry. Compared with the non-distended sham rats, uterine cervical distension resulted in a stimulus-dependent increase in electromyographic activity and the number of pERK-IR neurons that selectively located to the thoracolumbar segment, mostly in the deep dorsal and the central canal regions. The time course study demonstrated that spinal ERK activation peaked at 60 min with a slow decline for 120 min after uterine cervical distension stimulation. This study suggests that activation of spinal ERK might be involved in acute visceral pain arising from the uterine cervix. Copyright 2009 Elsevier Ltd. All rights reserved.

Mechanism of UES relaxation initiated by gastric air distension

PubMed Central

Medda, Bidyut K.; Shaker, Reza

2014-01-01

The aim of this study was to determine the mechanism of initiation of transient upper esophageal sphincter relaxation (TUESR) caused by gastric air distension. Cats (n = 31) were decerebrated, EMG electrodes were placed on the cricopharyngeus, a gastric fistula was formed, and a strain gauge was sewn on the lower esophageal sphincter (n = 8). Injection of air (114 ± 13 ml) in the stomach caused TUESR (n = 18) and transient lower esophageal sphincter relaxation (TLESR, n = 6), and this effect was not significantly (P > 0.05) affected by thoracotomy. Free air or bagged air (n = 6) activated TLESR, but only free air activated TUESR. Closure of the gastroesophageal junction blocked TUESR (9/9), but not TLESR (4/4), caused by air inflation of the stomach. Venting air from distal esophagus during air inflation of the stomach prevented TUESR (n = 12) but did not prevent air escape from the stomach to the esophagus (n = 4). Rapid injection of air on the esophageal mucosa always caused TUESR (9/9) but did not always (7/9) cause an increase in esophageal pressure. The time delay between the TUESR and the rapid air pulse was significantly more variable (P < 0.05) than the time delay between the rapid air pulse and the rise in esophageal pressure. We concluded that the TUESR caused by gastric air distension is dependent on air escape from the stomach, which stimulates receptors in the esophagus, but is not dependent on distension of the stomach or esophagus, or the TLESR. Therefore, the TUESR caused by gastric air distension is initiated by stimulation of receptors in the esophageal mucosa. PMID:24970778

Mechanism of UES relaxation initiated by gastric air distension.

PubMed

Lang, Ivan M; Medda, Bidyut K; Shaker, Reza

2014-08-15

The aim of this study was to determine the mechanism of initiation of transient upper esophageal sphincter relaxation (TUESR) caused by gastric air distension. Cats (n = 31) were decerebrated, EMG electrodes were placed on the cricopharyngeus, a gastric fistula was formed, and a strain gauge was sewn on the lower esophageal sphincter (n = 8). Injection of air (114 ± 13 ml) in the stomach caused TUESR (n = 18) and transient lower esophageal sphincter relaxation (TLESR, n = 6), and this effect was not significantly (P > 0.05) affected by thoracotomy. Free air or bagged air (n = 6) activated TLESR, but only free air activated TUESR. Closure of the gastroesophageal junction blocked TUESR (9/9), but not TLESR (4/4), caused by air inflation of the stomach. Venting air from distal esophagus during air inflation of the stomach prevented TUESR (n = 12) but did not prevent air escape from the stomach to the esophagus (n = 4). Rapid injection of air on the esophageal mucosa always caused TUESR (9/9) but did not always (7/9) cause an increase in esophageal pressure. The time delay between the TUESR and the rapid air pulse was significantly more variable (P < 0.05) than the time delay between the rapid air pulse and the rise in esophageal pressure. We concluded that the TUESR caused by gastric air distension is dependent on air escape from the stomach, which stimulates receptors in the esophagus, but is not dependent on distension of the stomach or esophagus, or the TLESR. Therefore, the TUESR caused by gastric air distension is initiated by stimulation of receptors in the esophageal mucosa. Copyright © 2014 the American Physiological Society.

Pneumatic Distension of Ventricular Mural Architecture Validated Histologically.

PubMed

Burg, M C; Lunkenheimer, P; Niederer, P; Brune, C; Redmann, K; Smerup, M; Spiegel, U; Becker, F; Maintz, D; Heindel, W; Anderson, R H

2016-11-01

Purpose: There are ongoing arguments as to how cardiomyocytes are aggregated together within the ventricular walls. We used pneumatic distension through the coronary arteries to exaggerate the gaps between the aggregated cardiomyocytes, analyzing the pattern revealed using computed tomography, and validating our findings by histology. Methods: We distended 10 porcine hearts, arresting 4 in diastole by infusion of cardioplegic solutions, and 4 in systole by injection of barium chloride. Mural architecture was revealed by computed tomography, measuring also the angulations of the long chains of cardiomyocytes. We prepared the remaining 2 hearts for histology by perfusion with formaldehyde. Results: Increasing pressures of pneumatic distension elongated the ventricular walls, but produced insignificant changes in mural thickness. The distension exaggerated the spaces between the aggregated cardiomyocytes, compartmenting the walls into epicardial, central, and endocardial regions, with a feathered arrangement of transitions between them. Marked variation was noted in the thicknesses of the parts in the different ventricular segments, with no visible anatomical boundaries between them. Measurements of angulations revealed intruding and extruding populations of cardiomyocytes that deviated from a surface-parallel alignment. Scrolling through the stacks of tomographic images revealed marked spiraling of the aggregated cardiomyocytes when traced from base to apex. Conclusion: Our findings call into question the current assumption that cardiomyocytes are uniformly aggregated together in a tangential fashion. There is marked heterogeneity in the architecture of the different ventricular segments, with the aggregated units never extending in a fully transmural fashion. Key Points: • Pneumographic computed tomography reveals an organized structure of the ventricular walls.• Aggregated cardiomyocytes form a structured continuum, with marked regional heterogeneity

When pain and hunger collide; psychological influences on differences in brain activity during physiological and non-physiological gastric distension.

PubMed

Coen, S J

2011-06-01

Functional neuroimaging has been used extensively in conjunction with gastric balloon distension in an attempt to unravel the relationship between the brain, regulation of hunger, satiety, and food intake tolerance. A number of researchers have also adopted a more physiological approach using intra-gastric administration of a liquid meal which has revealed different brain responses to gastric balloon distension. These differences are important as they question the utility and relevance of non-physiological models such as gastric balloon distension, especially when investigating mechanisms of feeding behavior such as satiety. However, an assessment of the relevance of physiological versus non-physiological gastric distension has been problematic due to differences in distension volumes between studies. In this issue of Neurogastroenterology and Motility, Geeraerts et al. compare brain activity during volume matched nutrient gastric distension and balloon distension in healthy volunteers. Gastric balloon distension activated the 'visceral pain neuromatrix'. This network of brain regions was deactivated during nutrient infusion, supporting the notion that brain activity during physiological versus non-physiological distension is indeed different. The authors suggest deactivation of the pain neuromatrix during nutrient infusion serves as a prerequisite for tolerance of normal meal volumes in health. © 2011 Blackwell Publishing Ltd.

Models of visceral pain: colorectal distension (CRD).

PubMed

Jones, R Carter W; Gebhart, G F

2004-09-01

The visceromotor response to balloon distension of the colon is a robust behavioral model of visceral nociception in rodents and is ideally suited for studying the visceral antinociceptive activity of drugs. This unit describes, in detail, quantification of this response with the use of electromyography in both rats and mice.

Establishment of model of visceral pain due to colorectal distension and its behavioral assessment in rats

PubMed Central

Yang, Jian-Ping; Yao, Ming; Jiang, Xing-Hong; Wang, Li-Na

2006-01-01

AIM: To establish a visceral pain model via colorectal distension (CRD) and to evaluate the efficiency of behavioral responses of CRD by measuring the score of abdominal withdrawal reflex (AWR) in rats. METHODS: Thirty-eight male SD rats weighing 180-240g were used to establish the visceral pain model. The rat was inserted intra-anally with a 7 cm long flexible latex balloon under ether anesthesia, and colorectal distensions by inflating the balloon with air were made 30 min after recovering from the anesthesia. Five AWR scores (AWR0 to AWR4) were used to assess the intensity of noxious visceral stimuli. It was regarded as the threshold of the minimal pressure (kPa) for abdominal flatting was induced by colorectal distension. RESULTS: A vigorous AWR to distension of the descending colon and rectum was found in 100% of the awake rats tested. The higher the pressure of distension, the higher the score of AWR. The distension pressures of 0, 2.00, 3.33, 5.33 and 8.00 kPa produced different AWR scores (P < 0.05). The pain threshold of AWR was constant for up to 80 min after the initial windup (first 1-3 distensions), the mean threshold was 3.69 ± 0.35 kPa. Systemic administration of morphine sulfate elevated the threshold of visceral pain in a dose-dependent and naloxone reversible manner. CONCLUSION: Scoring the AWR during colorectal distensions can assess the intensity of noxious visceral stimulus. Flatting of abdomen (AWR 3) to CRD as the visceral pain threshold is clear, constant and reliable. This pain model and its behavioral assessment are good for research on visceral pain and analgesics. PMID:16718770

Effects of Ultrasound-guided intra-articular ketorolac injection with capsular distension.

PubMed

Ahn, Jae Ki; Kim, Jongwoo; Lee, Sang Jae; Park, Yongbum; Bae, Byung; Lee, Woo

2015-01-01

Frozen shoulder is a painful condition with gradual onset and loss of range of motion in the glenohumeral joint. To investigate the efficacy of ultrasound(US)-guided intra-articular (IA) ketorolac injection with capsular distension compared with steroid injection alone in patients with frozen shoulder by assessing pain relief, functional improvements, and range of motion at 1,3 and 6 months after the last injections. Between January 2009 and December 2012, 121 patient were treated with US-guided IA steroid injection or IA ketorolac injection with capsular distension for frozen shoulder. Patients (n= 57) of US-guided IA steroid injection group were administered with a mixture of 0.5% lidocaine (4 ml) plus triamcinolone (40 mg/ml; 1 ml) and patients (n= 64) of US-guided IA ketorolac injection with capsular distension group were administered by using 0.5% lidocaine (19 mL) plus ketorolac (30 mg/ml; 1 mL) for capsular distension. Outcome measurement was assessed by Shoulder Pain and Disability Index (SPADI), Verbal Numeric pain Scale (VNS) and passive range of motion (ROM) before injections and at 1, 3 and 6 months after the last injections. We regarded the outcomes as a success if patients obtained significant pain relief (as measured by > 50% improvement in the VNS score and 20 point improvement in the SPASI) at 1, 3 and 6 months after the last injections. SPADI, VNS and passive ROM were improved 1, 3 and 6 months after the last injections in both groups. The statistical differences were not observed in SPADI, VNS between groups (p< 0.05). Successful treatment rate were not significantly different between the groups as well as in 1, 3 and 6 month outcomes. However, greater improvement was found in a matter of range of motion in patients receiving IA ketorolac injection with capsular distension than participants receiving US-guided IA steroid injection alone. Significant differences in improvement at 3 and 6 months were observed for shoulder passive abduction and

Estrogen replacement, vascular distensibility, and blood pressures in postmenopausal women.

PubMed

De Meersman, R E; Zion, A S; Giardina, E G; Weir, J P; Lieberman, J S; Downey, J A

1998-05-01

The pathogenesis of blood pressure (BP) rise in aging women remains unexplained, and one of the many incriminating factors may include abnormalities in arteriolar resistance vessels. The aim of this study was to determine the effects of unopposed estrogen on arteriolar distensibility, baroreceptor sensitivity (BRS), BP changes, and rate-pressure product (RPP). We tested the hypotheses that estrogen replacement therapy (ERT) enhances arteriolar distensibility and ameliorates BRS, which leads to decreases in BP and RPP. Postmenopausal women participated in a single-blind crossover study; the participants of this study, after baseline measurements, were randomly assigned to receive estrogen (ERT) or a drug-free treatment with a 6-wk washout period between treatments. The single-blind design was instituted because subjects become unblinded due to physiological changes (i.e., fluid shifts, weight gain, and secretory changes) associated with estrogen intake. However, investigators and technicians involved in data collection and analyses remained blind. After each treatment, subjects performed identical autonomic tests, during which electrocardiograms, beat-by-beat BPs, and respiration were recorded. The area under the dicrotic notch of the BP wave was used as an index of arteriolar distensibility. The magnitude of the reflex bradycardia after a precipitous rise in BP was used to determine BRS. Power spectral analysis of heart rate variability was used to assess autonomic activity. BPs were recorded from resistance vessels in the finger using a beat-by-beat photoplethysmographic device. RPP, a noninvasive marker of myocardial oxygen consumption, was calculated. Repeated-measures analyses of variance revealed a significantly enhanced arteriolar distensibility and BRS after ERT (P < 0.05). A trend of a lower sympathovagal balance at rest was observed after ERT, however, this trend did not reach statistical significance (P = 0.061) compared with the other treatments. The

Reversal of reflex pulmonary vasoconstriction induced by main pulmonary arterial distension.

PubMed

Juratsch, C E; Grover, R F; Rose, C E; Reeves, J T; Walby, W F; Laks, M M

1985-04-01

Distension of the main pulmonary artery (MPA) induces pulmonary hypertension, most probably by neurogenic reflex pulmonary vasoconstriction, although constriction of the pulmonary vessels has not actually been demonstrated. In previous studies in dogs with increased pulmonary vascular resistance produced by airway hypoxia, exogenous arachidonic acid has led to the production of pulmonary vasodilator prostaglandins. Hence, in the present study, we investigated the effect of arachidonic acid in seven intact anesthetized dogs after pulmonary vascular resistance was increased by MPA distention. After steady-state pulmonary hypertension was established, arachidonic acid (1.0 mg/min) was infused into the right ventricle for 16 min; 15-20 min later a 16-mg bolus of arachidonic acid was injected. MPA distension was maintained throughout the study. Although the infusion of arachidonic acid significantly lowered the elevated pulmonary vascular resistance induced by MPA distension, the pulmonary vascular resistance returned to control levels only after the bolus injection of arachidonic acid. Notably, the bolus injection caused a biphasic response which first increased the pulmonary vascular resistance transiently before lowering it to control levels. In dogs with resting levels of pulmonary vascular resistance, administration of arachidonic acid in the same manner did not alter the pulmonary vascular resistance. It is concluded that MPA distension does indeed cause reflex pulmonary vasoconstriction which can be reversed by vasodilator metabolites of arachidonic acid. Even though this reflex may help maintain high pulmonary vascular resistance in the fetus, its function in the adult is obscure.

Free-breathing black-blood CINE fast-spin echo imaging for measuring abdominal aortic wall distensibility: a feasibility study

NASA Astrophysics Data System (ADS)

Lin, Jyh-Miin; Patterson, Andrew J.; Chao, Tzu-Cheng; Zhu, Chengcheng; Chang, Hing-Chiu; Mendes, Jason; Chung, Hsiao-Wen; Gillard, Jonathan H.; Graves, Martin J.

2017-05-01

The paper reports a free-breathing black-blood CINE fast-spin echo (FSE) technique for measuring abdominal aortic wall motion. The free-breathing CINE FSE includes the following MR techniques: (1) variable-density sampling with fast iterative reconstruction; (2) inner-volume imaging; and (3) a blood-suppression preparation pulse. The proposed technique was evaluated in eight healthy subjects. The inner-volume imaging significantly reduced the intraluminal artifacts of respiratory motion (p  =  0.015). The quantitative measurements were a diameter of 16.3  ±  2.8 mm and wall distensibility of 2.0  ±  0.4 mm (12.5  ±  3.4%) and 0.7  ±  0.3 mm (4.1  ±  1.0%) for the anterior and posterior walls, respectively. The cyclic cross-sectional distensibility was 35  ±  15% greater in the systolic phase than in the diastolic phase. In conclusion, we developed a feasible CINE FSE method to measure the motion of the abdominal aortic wall, which will enable clinical scientists to study the elasticity of the abdominal aorta.

Effects of mosapride citrate, a 5-HT4-receptor agonist, on gastric distension-induced visceromotor response in conscious rats.

PubMed

Seto, Yasuhiro; Yoshida, Naoyuki; Kaneko, Hiroshi

2011-01-01

Mosapride citrate (mosapride), a prokinetic agent with 5-HT(4)-receptor agonistic activity, is known to enhance gastric emptying and alleviate symptoms in patients with functional dyspepsia (FD). As hyperalgesia and delayed gastric emptying play an important role in the pathogenesis of FD, we used in this study balloon gastric distension to enable abdominal muscle contractions and characterized the visceromotor response (VMR) to such distension in conscious rats. We also investigated the effects of mosapride on gastric distension-induced VMR in the same model. Mosapride (3-10 mg/kg, p.o.) dose-dependently inhibited gastric distension-induced VMR in rats. However, itopride even at 100 mg/kg failed to inhibit gastric distension-induced VMR in rats. Additionally, a major metabolite M1 of mosapride, which possesses 5-HT(3)-receptor antagonistic activity, inhibited gastric distension-induced VMR. The inhibitory effect of mosapride on gastric distension-induced visceral pain was partially, but significantly inhibited by SB-207266, a selective 5-HT(4)-receptor antagonist. This study shows that mosapride inhibits gastric distension-induced VMR in conscious rats. The inhibitory effect of mosapride is mediated via activation of 5-HT(4) receptors and blockage of 5-HT(3) receptors by a mosapride metabolite. This finding indicates that mosapride may be useful in alleviating FD-associated gastrointestinal symptoms via increase in pain threshold.

Antinociceptive action against colonic distension by brain orexin in conscious rats.

PubMed

Okumura, Toshikatsu; Nozu, Tsukasa; Kumei, Shima; Takakusaki, Kaoru; Miyagishi, Saori; Ohhira, Masumi

2015-02-19

Increasing evidence has suggested that brain orexins are implicated in a wide variety of physiological functions. With regard to gastrointestinal functions, orexin-A acts centrally to regulate gastrointestinal functions such as gastric and pancreatic secretion, and gastrointestinal motility. Visceral sensation is also known as one of key gastrointestinal functions which are controlled by the central nervous system. Little is, however, known about a role of central orexin in visceral sensation. This study was therefore performed to clarify whether brain orexin may be involved in the process of visceral sensation. Visceral sensation was evaluated by colonic distension-induced abdominal withdrawal reflex (AWR) in conscious rats. Intracisternally administered orexin-A dose-dependently increased the threshold volume of colonic distension-induced AWR. In contrast, neither intraperitoneal injection of orexin-A nor intracisternal orexin-B altered the threshold volume. While intracisternal SB334867, an orexin 1 receptor antagonist, by itself failed to change the threshold volume, SB334867 injected centrally completely blocked the morphine-induced antinociceptive action against colonic distension. These results suggest for the first time that orexin-A specifically acts centrally in the brain to enhance antinociceptive response to colonic distension. We would furthermore suggest that endogenous orexin-A indeed mediates the antinociceptive effect of morphine on visceral sensation through the orexin 1 receptors. All these evidence might indicate that brain orexin plays a role in the pathophysiology of functional gastrointestinal disorders such as irritable bowel syndrome because visceral hypersensitivity of the gut is considered to play a vital role in the diseases. Copyright © 2014 Elsevier B.V. All rights reserved.

Transitional Flow in an Arteriovenous Fistula: Effect of Wall Distensibility

NASA Astrophysics Data System (ADS)

McGah, Patrick; Leotta, Daniel; Beach, Kirk; Aliseda, Alberto

2012-11-01

Arteriovenous fistulae are created surgically to provide adequate access for dialysis in patients with end-stage renal disease. Transitional flow and the subsequent pressure and shear stress fluctuations are thought to be causative in the fistula failure. Since 50% of fistulae require surgical intervention before year one, understanding the altered hemodynamic stresses is an important step toward improving clinical outcomes. We perform numerical simulations of a patient-specific model of a functioning fistula reconstructed from 3D ultrasound scans. Rigid wall simulations and fluid-structure interaction simulations using an in-house finite element solver for the wall deformations were performed and compared. In both the rigid and distensible wall cases, transitional flow is computed in fistula as evidenced by aperiodic high frequency velocity and pressure fluctuations. The spectrum of the fluctuations is much more narrow-banded in the distensible case, however, suggesting a partial stabilizing effect by the vessel elasticity. As a result, the distensible wall simulations predict shear stresses that are systematically 10-30% lower than the rigid cases. We propose a possible mechanism for stabilization involving the phase lag in the fluid work needed to deform the vessel wall. Support from an NIDDK R21 - DK08-1823.

The impact of gastric distension on the lower esophageal sphincter and its exposure to acid gastric juice.

PubMed

Ayazi, Shahin; Tamhankar, Anand; DeMeester, Steven R; Zehetner, Joerg; Wu, Calvin; Lipham, John C; Hagen, Jeffrey A; DeMeester, Tom R

2010-07-01

The lower esophageal sphincter (LES) in patients with gastroesophageal reflux disease often has a low resting pressure and a short abdominal length. The mechanism by which this occurs is unknown. We hypothesize that gastric distension causes progressive effacement of the abdominal portion of the LES, exposing it to acid injury resulting in mucosal and sphincter damage. Our aim was to assess in normal subjects the effect of gastric distension on the LES length and pressure and its exposure to acid gastric juice. Eleven asymptomatic volunteers had their LES length and pressure measured before and during gastric distension. The location of the pH step-up point (shift from gastric pH to a pH >4) was also measured before and after distension. Progressive gastric distension with air resulted in progressive shortening of LES (R = 0.89, P < 0.0001). After infusion of 750 cc of air there was a significant reduction in the median LES length from 4 to 2.6 cm (P = 0.001). This change occurred in the abdominal length of the LES (2.6-1.4 cm [P = 0.001]) and not in the thoracic length. At rest the pH step-up point was 0.5 cm above the lower border of the LES and with distension moved a median of 1 cm cephalad within the LES. Simultaneously with the loss of length there was a reduction in LES pressure (27.4-23.4 mm Hg, P = 0.02). Gastric distension causes progressive shortening of the abdominal length of the LES and a reduction in its pressure. The process exposes the effaced mucosa and sphincter to acid gastric juice.

Distension-Induced Gastric Contraction is Attenuated in an Experimental Model of Gastric Restraint

PubMed Central

Lu, Xiao; Guo, Xiaomei; Mattar, Samer G.; Navia, Jose A.

2010-01-01

Background Gastric distension has important implications for motility and satiety. The hypothesis of this study was that distension affects the amplitude and duration of gastric contraction and that these parameters are largely mediated by efferent vagus stimulation. Methods A novel isovolumic myograph was introduced to test these hypotheses. The isovolumic myograph isolates the stomach and records the pressure generated by the gastric contraction under isovolumic conditions. Accordingly, the phasic changes of gastric contractility can be documented. A group of 12 rats were used under in vivo conditions and isolated ex vivo conditions and with two different gastric restraints (small and large) to determine the effect of degree of restraint. Results The comparison of the in vivo and ex vivo contractility provided information on the efferent vagus mediation of gastric contraction, i.e., the in vivo amplitude and duration reached maximum of 12.6 ± 2.7 mmHg and 19.8 ± 5.6 s in contrast to maximum of 5.7 ± 0.9 mmHg and 7.3 ± 1.3 s in ex vivo amplitude and duration, respectively. The comparison of gastric restraint and control groups highlights the role of distension on in vivo gastric contractility. The limitation of gastric distension by restraint drastically reduced the maximal amplitude to below 2.9 ± 0.2 mmHg. Conclusions The results show that distension-induced gastric contractility is regulated by both central nervous system and local mechanisms with the former being more substantial. Furthermore, the gastric restraint significantly attenuates gastric contractility (decreased amplitude and shortened duration of contraction) which is mediated by the efferent vagus activation. These findings have important implications for gastric motility and physiology and may improve our understanding of satiety. PMID:20706803

Regional aortic distensibility and its relationship with age and aortic stenosis: a computed tomography study.

PubMed

Wong, Dennis T L; Narayan, Om; Leong, Darryl P; Bertaso, Angela G; Maia, Murilo G; Ko, Brian S H; Baillie, Timothy; Seneviratne, Sujith K; Worthley, Matthew I; Meredith, Ian T; Cameron, James D

2015-06-01

Aortic distensibility (AD) decreases with age and increased aortic stiffness is independently associated with adverse cardiovascular outcomes. The association of severe aortic stenosis (AS) with AD in different aortic regions has not been evaluated. Elderly subjects with severe AS and a cohort of patients without AS of similar age were studied. Proximal aortic cross-sectional-area changes during the cardiac cycle were determined using retrospective-ECG-gating on 128-detector row computed-tomography. Using oscillometric-brachial-blood-pressure measurements, the AD at the ascending-aorta (AA), proximal-descending-aorta (PDA) and distal-descending-aorta (DDA) was determined. Linear mixed effects modelling was used to determine the association of age and aortic stenosis on regional AD. 102 patients were evaluated: 36 AS patients (70-85 years), 24 AS patients (>85 years) and 42 patients without AS (9 patients <50 years, 20 patients between 51-70 years and 13 patients 70-85 years). When comparing patients 70-85 years, AA distensibility was significantly lower in those with AS compared to those without AS (0.9 ± 0.9 vs. 1.4 ± 1.1, P = 0.03) while there was no difference in the PDA (1.0 ± 1.1 vs. 1.0 ± 1.2, P = 0.26) and DDA (1.1 ± 1.2 vs. 1.2 ± 0.8, P = 0.97). In patients without AS, AD decreased with age in all aortic regions (P < 0.001). The AA in patients <50 years were the most distensible compared to other aortic regions. There is regional variation in aortic distensibility with aging. Patients with aortic stenosis demonstrated regional differences in aortic distensibility with lower distensibility demonstrated in the proximal ascending aorta compared to an age-matched cohort.

The Influence of Blood Pressure on Fetal Aortic Distensibility: An Animal Validation Study.

PubMed

Wohlmuth, Christoph; Moise, Kenneth J; Papanna, Ramesha; Gheorghe, Ciprian; Johnson, Anthony; Morales, Yisel; Gardiner, Helena M

2018-01-01

Aortic distension waveforms describe the change in diameter or cross-sectional area over the cardiac cycle. We aimed to validate the association of aortic fractional area change (AFAC) with blood pressure (BP) in a fetal lamb model. Four pregnant ewes underwent open fetal surgery under general anesthesia at 107-120 gestational days. A 4-Fr catheter was introduced into the fetal femoral artery and vein, or the carotid artery and jugular vein. The thoracic aorta was imaged using real-time ultrasound; AFAC was calculated using offline speckle tracking software. Measurements of invasive BP and AFAC were obtained simultaneously and averaged over 10 cardiac cycles. BP was increased by norepinephrine infusion and the association of aortic distensibility with BP was assessed. Baseline measurements were obtained from 4 lambs, and changes in aortic distensibility with increasing BP were recorded from 3 of them. A positive correlation was found between AFAC and systolic BP (r = 0.692, p = 0.001), diastolic BP (r = 0.647, p = 0.004), mean BP (r = 0.692, p = 0.001), and BP amplitude (r = 0.558, p = 0.016) controlled for heart rate. No association was found between BP and maximum or minimum aortic area. AFAC provides a quantifiable measure of aortic distensibility and correlates with systolic BP, diastolic BP, mean BP, and BP amplitude in a fetal lamb model. © 2017 S. Karger AG, Basel.

[The respiratory muscles in emphysema. The effects of thoracic distension].

PubMed

Cassart, M; Estenne, M

2000-04-01

Besides increasing the work of ventilation, emphysema increases lung volume which in itself has a deleterious effect on the inspiratory muscles. We review here the effects of an acute change in lung volume on the configuration of the rib cage and muscle function. We also discuss the effects of the chronic distension associated with emphysema. The effects produced by changes in muscle length and configuration on the mechanical force and action of inspiratory muscles is detailed with particular focus on the diaphragm and its structural adaptations to experimental emphysema. We also analyze the activation pattern of inspiratory and expiratory muscles during the breathing process in patients with emphysema. Finally, we discuss the effects of single-lung transplantation and reduction surgery on chest distension and improved inspiratory muscle function.

Distension of the uterus induces HspB1 expression in rat uterine smooth muscle.

PubMed

White, B G; MacPhee, D J

2011-11-01

The uterine musculature, or myometrium, demonstrates tremendous plasticity during pregnancy under the influences of the endocrine environment and mechanical stresses. Expression of the small stress protein heat shock protein B1 (HspB1) has been reported to increase dramatically during late pregnancy, a period marked by myometrial hypertrophy caused by fetal growth-induced uterine distension. Thus, using unilaterally pregnant rat models and ovariectomized nonpregnant rats with uteri containing laminaria tents to induce uterine distension, we examined the effect of uterine distension on myometrial HspB1 expression. In unilaterally pregnant rats, HspB1 mRNA and Ser(15)-phosphorylated HspB1 (pSer(15) HspB1) protein expression were significantly elevated in distended gravid uterine horns at days 19 and 23 (labor) of gestation compared with nongravid horns. Similarly, pSer(15) HspB1 protein in situ was only readily detectable in the distended horns compared with the nongravid horns at days 19 and 23; however, pSer(15) HspB1 was primarily detectable in situ at day 19 in membrane-associated regions, while it had primarily a cytoplasmic localization in myometrial cells at day 23. HspB1 mRNA and pSer(15) HspB1 protein expression were also markedly increased in ovariectomized nonpregnant rat myometrium distended for 24 h with laminaria tents compared with empty horns. Therefore, uterine distension plays a major role in the stimulation of myometrial HspB1 expression, and increased expression of this small stress protein could be a mechanoadaptive response to the increasing uterine distension that occurs during pregnancy.

Carotid artery intima-media thickness and distensibility in children and adolescents: reference values and role of body dimensions.

PubMed

Doyon, Anke; Kracht, Daniela; Bayazit, Aysun K; Deveci, Murat; Duzova, Ali; Krmar, Rafael T; Litwin, Mieczyslaw; Niemirska, Anna; Oguz, Berna; Schmidt, Bernhard M W; Sözeri, Betul; Querfeld, Uwe; Melk, Anette; Schaefer, Franz; Wühl, Elke

2013-09-01

Carotid intima-media thickness (cIMT) and carotid artery distensibility are reliable screening methods for vascular alterations and the assessment of cardiovascular risk in adult and pediatric cohorts. We sought to establish an international reference data set for the childhood and adolescence period and explore the impact of developmental changes in body dimensions and blood pressure (BP) on carotid wall thickness and elasticity. cIMT, the distensibility coefficient, the incremental modulus of elasticity, and the stiffness index β were assessed in 1155 children aged 6 to 18 years and sex-specific reference charts normalized to age or height were constructed from 1051 nonobese and nonhypertensive children. The role of body dimensions, BP, and family history, as well as the association between cIMT and distensibility, was investigated. cIMT increased and distensibility decreased with age, height, body mass index, and BP. A significant sex difference was apparent from the age of 15 years. Age- and height-normalized cIMT and distensibility values differed in children who are short or tall for their age. By stepwise multivariate analysis, standardized systolic BP and body mass index were independently positively associated with cIMT SD scores (SDS). Systolic BP SDS independently predicted all distensibility measures. Distensibility coefficient SDS was negatively and β SDS positively associated with cIMT SDS, whereas incremental modulus of elasticity was independent of cIMT. Morphological and functional aspects of the common carotid artery are particularly influenced by age, body dimensions, and BP. The reference charts established in this study allow to accurately compare vascular phenotypes of children with chronic conditions with those of healthy children.

Study of the effect of jejuno-ileal distension on the motor activity of the stomach with evidence of "entero-gastric inhibitory reflex".

PubMed

Shafik, Ahmed; Shafik, Ali A; el-Sibai, Olfat

2003-01-01

In chronic constipation due to delayed colonic transit, stasis of the ileal contents with resulting ileal distension may occur. The current study investigated the effect of ileal and jejunal distension on the gastric motility, aiming at elucidating the possible existence of a relationship and its role in the flow through the gut. The response of the gastric pressure to ileal and jejunal balloon distension in increments of 2 mL of saline was recorded in 12 mongrel dogs. The test was repeated after separate local anesthetization of the ileum, jejunum and stomach. 2- and 4-mL ileal balloon distension produced no significant gastric pressure response, while 6- and up to 10-mL distension effected decrease of the antral and corporeal pressures (p < 0.05, p < 0.05, respectively). Jejunal distension produced a gastric pressure decline (p < 0.05) with 4 and up to 10 mL of saline. The gastric pressure decrease did not show significant changes with the various distending volumes. It was maintained as long as ileal or jejunal distension was continued. Distension of the anesthetized ileum or jejunum caused no gastric pressure changes, nor did ileal or jejunal distension produce pressure changes in the anesthetized stomach. The gastric pressure decline and presumably hypotonia upon ileal or jejunal distension with big volumes postulate a reflex relationship which we call "entero-gastric inhibitory reflex". The small intestine is suggested to slow down gastric emptying through this reflex. A balance is thus created between chyme delivery from the stomach and chyme processing by the small intestine. Reflex derangement in neurogenic and myogenic diseases may result in gastrointestinal disorders, a point that needs to be investigated.

Supraspinal control of external anal sphincter motility: effects of vesical distension in humans and cats.

PubMed

Vitton, V; Grimaud, J-C; Bouvier, M; Abysique, A

2006-11-01

A pontine centre located near the micturition centre controlling external anal sphincter (EAS) motility via noradrenergic neurones has been described in cats. The aim of this study was to determine (i) whether a similar centre controls EAS motility in humans and (ii) whether this centre is involved in vesico-sphincteric reflexes in cats and humans. The effects of an alpha-1-adrenoceptor antagonist (nicergoline) and those of vesical distension on the electrical activity of the EAS were studied in paraplegic and non-paraplegic volunteers. The effects of vesical distension by injecting saline at physiological levels on the responses of the EAS to pudendal nerve stimulation were investigated in intact cats and cats with nerve sections. In non-paraplegic subjects, nicergoline and vesical distension abolished the activity of the EAS. These effects were no longer observed in paraplegic patients. In cats, vesical distension inhibited the reflex response of the EAS to pudendal nerve stimulation. This vesico-sphincteric reflex, which was no longer observed in spinal animals, persisted after nicergoline injection. These findings indicate that in humans, there exists a supra-spinal centre facilitating the tonic activity of the EAS via noradrenergic neurones not involved in the inhibitory vesico-sphincteric reflex.

Structural and vascular response of normal and obstructed rabbit whole bladders to distension.

PubMed

Matsumoto, Seiji; Chichester, Paul; Kogan, Barry A; Levin, Robert M

2003-12-01

To investigate the structural and morphologic effect of distension after partial outlet obstruction in rabbits. Thirty male New Zealand white rabbits were separated into two groups: control (sham) and partial outlet obstruction (3 weeks). Three rabbits from each group were distended to 5%, 25%, 50%, 100%, and 125% of capacity. Each bladder was fixed at the volume in buffered formalin for 6 to 8 hours. Sections of dorsal and ventral bladder were blocked, and cross sections were evaluated. Quantitative morphometry was performed, and CD31 immunohistochemistry was used to characterize the vascularity. Partial outlet obstruction resulted in increased bladder weight and capacity and increased thickness of the mucosa, submucosa, detrusor, and serosa. In the control bladder, the greatest thinning was seen between 5% and 25% capacity, and in the obstructed group, the greatest thinning occurred between 25% and 50%. The level of vascular collapse was significantly greater for the control bladders than for the obstructed bladders at all levels of distension. Finally, the obstructed bladders showed a significantly greater level of vascularity in the submucosa than the control bladders. Normal bladder distension resulted in significant morphologic changes when the bladder was distended to 25% of capacity but changed relatively little between 25% and 125%. However, distension of the obstructed bladder resulted in significant morphologic changes when the bladder was distended from 25% to 50% of capacity but changed relatively little between 50% and 125%.

Colon Hypersensitivity to Distension, Rather Than Excessive Gas Production, Produces Carbohydrate-Related Symptoms in Individuals With Irritable Bowel Syndrome.

PubMed

Major, Giles; Pritchard, Sue; Murray, Kathryn; Alappadan, Jan Paul; Hoad, Caroline L; Marciani, Luca; Gowland, Penny; Spiller, Robin

2017-01-01

reached the symptom threshold after inulin intake, peak symptom intensity correlated with peak colonic gas (r = 0.57; P < .05). Changes in MRI features and peak breath hydrogen levels were similar in patients who did and did not reach the symptom threshold. Patients with IBS and healthy individuals without IBS (controls) have similar physiological responses after intake of fructose or inulin; patients reported symptoms more frequently after inulin than controls. In patients with a response to inulin, symptoms related to levels of intraluminal gas, but peak gas levels did not differ significantly between responders, nonresponders, or controls. This indicates that colonic hypersensitivity to distension, rather than excessive gas production, produces carbohydrate-related symptoms in patients with IBS. Clinicaltrials.gov no: NCT01776853. Copyright © 2017 AGA Institute. Published by Elsevier Inc. All rights reserved.

Submucosal reflexes: distension-evoked ion transport in the guinea pig distal colon.

PubMed

Frieling, T; Wood, J D; Cooke, H J

1992-07-01

Muscle-stripped segments of distal colon from guinea pigs were mounted in modified flux chambers to determine the effect of distension on mucosal secretion. Ion secretion was monitored as changes in short-circuit current (Isc). Distending forces were pressure gradients established by controlled reduction in liquid volume of the submucosal compartment of the chamber. Volume removal for 10 s or 5 min evoked a monophasic or biphasic increase in Isc, which returned to baseline within 5-20 min. The amplitude of the response correlated with the volume removed and was reduced by bumetanide and Cl-free solutions but not by tetraethylammonium or amiloride. Tetrodotoxin and atropine also suppressed the response. Neither the nicotinic receptor antagonist mecamylamine, the 5-hydroxytryptamine3 (5-HT3) receptor antagonist ICS 205-930, or the prostaglandin synthesis inhibitor piroxicam altered the response. Addition of prostaglandin D2 to the submucosal bath significantly enhanced the response. The results suggest that distension of the colon evokes anion secretion by activation of reflex circuits with cholinergic neurons and muscarinic synapses. Prostaglandins and 5-hydroxytryptamine acting at 5-HT3 receptors appear not to be signal substances in the reflex pathway, which evokes the secretory response to distension.

Renal clearance studies of effect of left atrial distension in the dog.

NASA Technical Reports Server (NTRS)

Kinney, M. J.; Discala, V. A.

1972-01-01

Investigation of the water diuresis of left atrial distension in 16 dogs on the basis of clearance studies employing hydration, chronic and acute salt loading, deoxycorticosterone (DOCA) in excess, and distal tubular nephron blockade with diuretics. The diuresis was found in hydrated and salt-loaded dogs and was independent of DOCA and presumed renin depletion. It was not found in five dogs after distal tubular blockade. No significant reproducible saluresis was ever documented. The water diuresis was always stopped by exogenous vasopressin (seven dogs). Antidiuretic hormone inhibition with distal tubular nephron water permeability changes appears to be the sole mechanism of the diuresis of left atrial distension in the dog.

Response of cricopharyngeus muscle to esophageal stimulation by mechanical distension and acid and bile perfusion.

PubMed

Chernichenko, Natalya; Woo, Jeong-Soo; Hundal, Jagdeep S; Sasaki, Clarence T

2011-02-01

The aim of this study was to identify the response of the cricopharyngeus muscle (CPM) to esophageal stimulation by intraluminal mechanical distension and intraluminal acid and bile perfusion. In 3 adult pigs, electromyographic (EMG) activity of the CPM was recorded at baseline and after esophageal stimulation at 3 levels: proximal, middle, and distal. The esophagus was stimulated with 20-mL balloon distension and intraluminal perfusion of 40 mL 0.1N hydrochloric acid, taurocholic acid (pH 1.5), and chenodeoxycholic acid (pH 7.4) at the rate of 40 mL/min. The EMG spike density was defined as peak-to-peak spikes greater than 10 microV averaged over 10-ms intervals. In all 3 animals, the spike density at baseline was 0. The spike densities increased after proximal and middle distensions to 15.2 +/- 1.5 and 5.1 +/- 1.2 spikes per 10 ms, respectively. No change in CPM EMG activity occurred after distal distension. The spike density following intraluminal perfusion with hydrochloric acid at the distal level was 10.1 +/- 1.1 spikes per 10 ms. No significant change in CPM EMG activity occurred after acid perfusion at the middle and proximal levels. No change in CPM EMG activity occurred after intraluminal esophageal perfusion with either taurocholic acid or chenodeoxycholic acid. Proximal esophageal distension, as well as distal intraluminal acid perfusion, appeared to be important mechanisms in generation of CPM activity. Bile acids, on the other hand, failed to evoke such CPM activity. The data suggest that transpyloric refluxate may not be significant enough to evoke the CPM protective sphincteric function, thereby placing supraesophageal structures at risk of bile injury.

Effects of gastric distension and infusion of umami and bitter taste stimuli on vagal afferent activity.

PubMed

Horn, Charles C; Murat, Chloé; Rosazza, Matthew; Still, Liz

2011-10-24

Until recently, sensory nerve pathways from the stomach to the brain were thought to detect distension and play little role in nutritional signaling. Newer data have challenged this view, including reports on the presence of taste receptors in the gastrointestinal lumen and the stimulation of multi-unit vagal afferent activity by glutamate infusions into the stomach. However, assessing these chemosensory effects is difficult because gastric infusions typically evoke a distension-related vagal afferent response. In the current study, we recorded gastric vagal afferent activity in the rat to investigate the possibility that umami (glutamate, 150 mM) and bitter (denatonium, 10 mM) responses could be dissociated from distension responses by adjusting the infusion rate and opening or closing the drainage port in the stomach. Slow infusions of saline (5 ml over 2 min, open port) produced no significant effects on vagal activity. Using the same infusion rate, glutamate or denatonium solutions produced little or no effects on vagal afferent activity. In an attempt to reproduce a prior report that showed distention and glutamate responses, we produced a distension response by closing the exit port. Under this condition, response to the infusion of glutamate or denatonium was similar to saline. In summary, we found little or no effect of gastric infusion of glutamate or denatonium on gastric vagal afferent activity that could be distinguished from distension responses. The current results suggest that sensitivity to umami or bitter stimuli is not a common property of gastric vagal afferent fibers. Copyright © 2011 Elsevier B.V. All rights reserved.

Assessment of visceral pain-related pseudo-affective responses to colorectal distension in mice by intracolonic manometric recordings.

PubMed

Arvidsson, Susanne; Larsson, Marie; Larsson, Håkan; Lindström, Erik; Martinez, Vincente

2006-02-01

Recently, a new manometric method has been proposed to quantify visceromotor responses (VMR) to colorectal distension (CRD) in rats. This method is based on monitoring pressure changes within the distending balloon during CRD. This study assesses the applicability of such a technique to the quantification of VMRs to CRD in mice. Electrical activity of the abdominal muscles and pressure changes within the distending balloon (mechanical response) were simultaneously recorded in conscious mice during CRD (phasic ascending, 10-80 mm Hg, or repetitive, 55 mm Hg). There was a clear stimulus-response relationship with a strong correlation between electrical and mechanical responses during the ascending (r(2) = 0.899, n = 7) or repetitive phasic CRD (r(2) = 0.926, n = 8). Repetitive phasic distensions (55 mm Hg) increased the mechanical and electrical responses by 71 +/- 20% and 42 +/- 16%, respectively (pulses 10-12 vs. 1-3; n = 8, both P < .01). Atropine (0.5 or 1 mg/kg, subcutaneously) did not affect the mechanical response to CRD. The mu-opioid agonist, fentanyl (0.05 mg/kg, subcutaneously), completely prevented the sensitizing response associated to repetitive distensions. These results show that noninvasive, surgery-free manometry of intracolonic pressure is a reliable method to assess VMRs to CRD in mice. The analgesic effect of compounds could be determined, indicating that the method can be used in pharmacologic studies. The model presented to assess visceral pain in mice allows a broad use of this species in pharmacological studies and will be of use in the characterization of potential targets and new drugs for the treatment of human pathologies with visceral pain arising from the gut as a significant component.

Commentary on: "Vascular distensibilities have minor effects on intracardiac shunt patterns in reptiles" by Filogonio et al. (2017).

PubMed

Hillman, Stanley S; Hedrick, Michael S; Kohl, Zachary F

2017-06-01

The recent study by Filogonio et al. (2017) suggested that net cardiac shunt patterns in two species of reptiles (Trachemys scripta and Crotalus durissus) were not significantly influenced by the vascular distensibilities of the systemic and pulmonary vasculatures. This is in contrast to a previously published study (Hillman et al., 2014) in the toad (Rhinella marina) in which net cardiac shunts were predicted primarily by the physical properties of vascular distensibility rather than physiological control of resistance of the systemic and pulmonary vasculature. We analyze the data and conclusions reached by Filogonio et al. (2017) regarding the role of vascular distensibilities in determining net cardiac shunt patterns in reptiles in comparison with toads. In our view, the conclusions reached by Filogonio et al. (2017) are not supported by the data primarily because vascular distensibilities were not measured in the reptiles analyzed in their study. Copyright © 2017 Elsevier GmbH. All rights reserved.

Intestinal electrical stimulation improves delayed gastric emptying and vomiting induced by duodenal distension in dogs.

PubMed

Xu, J; Chen, J D Z

2008-03-01

The aim of this study was to investigate the effects of short-pulse intestinal electrical stimulation (IES) on duodenal distention-induced delayed gastric emptying and vomiting in dogs and its possible mechanisms. The study was performed in 12 dogs with jejunal electrodes and a duodenal cannula in three separate experiments to investigate the effects of IES on duodenal distension (DD)-induced delayed gastric emptying and discomfort signs, vagal efferent activity, and jejunal tone. We found that: (i) IES significantly accelerated gastric emptying of liquid delayed by distension (18.05 +/- 4.06%vs. 7.18 +/- 1.99%, P = 0.036 at 60 min). (ii) IES significantly reduced vomiting and discomfort/pain induced by distension. The average signs score was 15.33 +/- 1.37 during distension which decreased to 6.50 +/- 0.91 (P = 0.0002) with IES. (iii) IES did not change vagal afferent activity, which was assessed by the spectral analysis of the heart rate variability. (iv) IES decreased jejunal tone. In conclusion, IES with parameters commonly used in gastric electrical stimulation for nausea and vomiting associated with gastroparesis improves DD-induced delayed gastric emptying and prevents DD-induced vomiting and discomfort signs. Further studies are warranted to investigate the therapeutic potential of IES for gastrointestinal symptoms associated with disturbances in motility and sensory function in small intestine.

Lattice Boltzmann method for simulating the viscous flow in large distensible blood vessels

NASA Astrophysics Data System (ADS)

Fang, Haiping; Wang, Zuowei; Lin, Zhifang; Liu, Muren

2002-05-01

A lattice Boltzmann method for simulating the viscous flow in large distensible blood vessels is presented by introducing a boundary condition for elastic and moving boundaries. The mass conservation for the boundary condition is tested in detail. The viscous flow in elastic vessels is simulated with a pressure-radius relationship similar to that of the pulmonary blood vessels. The numerical results for steady flow agree with the analytical prediction to very high accuracy, and the simulation results for pulsatile flow are comparable with those of the aortic flows observed experimentally. The model is expected to find many applications for studying blood flows in large distensible arteries, especially in those suffering from atherosclerosis, stenosis, aneurysm, etc.

The effect of rectal distension on bladder function in patients with overactive bladder.

PubMed

Akl, Mohamed N; Jacob, Kristina; Klauschie, Jennifer; Crowell, Michael D; Kho, Rosanne M; Cornella, Jeffrey L

2012-04-01

To investigate the effect of rectal distension on bladder sensation volumes and the number of detrusor contractions in patients with overactive bladder (OAB) symptoms. A prospective randomized study included patients with OAB symptoms. Multichannel urodynamic studies were completed with and without rectal balloon distension. Bladder sensation volumes and detrusor contractions were compared. Twenty-six patients were included in the study. The mean age was 67 years and mean BMI was 28.3 kg/m(2) . Bladder sensation volumes were lower with rectal distention as follows: normal desire to void (139 ml SD, ±114 vs. 197 ml SD ±150, P = 0.01), strong desire to void (260 ml SD ±171 vs. 330 ml SD ±172, P = 0.01), and maximum cystometric capacity (326 ml SD ±183 vs. 403 ml SD ±180, P = 0.0001). There was no difference in the number of detrusor contractions or the bladder volume at which the first detrusor contraction had occurred with and without rectal distension. Rectal distention in patients with OAB symptoms significantly lowered bladder sensation volumes (normal desire, strong desire, and maximal capacity). Copyright © 2012 Wiley Periodicals, Inc.

Colorectal distension-induced pseudoaffective changes as indices of nociception in the anesthetized female rat: morphine and strain effects on visceral sensitivity.

PubMed

Sivarao, Digavalli V; Langdon, Shaun; Bernard, Christopher; Lodge, Nicholas

2007-01-01

Colorectal distension of a sufficient intensity evokes several characteristic postural, visceromotor and cardiovascular reflexes in conscious rats that have been extensively utilized for testing putative visceral analgesics. The neural circuitry for these reflexes is encompassed within the spinobulbar region and continues to be robust even after decerebration. Yet, these are not consistently replicated in anesthetized animals, presumably due to medullary depression. In the following studies, we tested the hypothesis that a carefully chosen anesthetic regimen can replicate the pattern of pseudoaffective responses seen in awake animals. Female rats were anesthetized with methohexital sodium and equipped with arterial and venous catheters, a colorectal balloon and abdominal wire electrodes. Subsequent anesthesia was maintained with urethane. Colorectal distension produced clear changes in visceromotor and cardiovascular indices that not only mimicked responses to distension seen in conscious rats, but also importantly, showed a comparable stimulus sensitivity and stability. Morphine (ED(50), 0.17 mg/kg, iv) was highly efficacious in attenuating response in a dose-dependent and naloxone-selective manner. Using this model, we compared three commonly used rat strains (Wistar, Wistar-Kyoto and Sprague-Dawley) for distension-mediated responses. Whereas Wistar-Kyoto rats were significantly hyper-responsive to distension, the sensory threshold for distension was nearly identical across strains. Thus, we report an anesthetized female rat model that replicates characteristic responses associated with visceral pain in conscious rats and its modulation by known factors like analgesia and strain. These findings provide a simple insensate model for testing novel visceral analgesics while eliminating postoperative recovery and motion-related artifact typically associated with colorectal distension studies in conscious rats. Thus, a viable and humane alternative to visceral

Duration of breast feeding and arterial distensibility in early adult life: population based study.

PubMed

Leeson, C P; Kattenhorn, M; Deanfield, J E; Lucas, A

2001-03-17

To test the hypothesis that duration of breast feeding is related to changes in vascular function relevant to the development of cardiovascular disease. Population based observational study. Cambridge. 331 adults (171 women, 160 men) aged between 20 and 28 years, born in Cambridge Maternity Hospital. Distensibility of brachial artery, type and duration of infant feeding, current lipid profile, and other cardiovascular risk factors. The longer the period of breast feeding the less distensible the artery wall in early adult life, with no sex differences (regression coefficient = -3.93 micrometer/month, 95% confidence interval -7.29 to -0.57, P=0.02). However, in those breast fed for less than four months, arterial distensibility was not significantly reduced compared with an exclusively formula fed group. The vascular changes observed were not explained by alterations in plasma cholesterol concentration in adult life. Breast feeding in infancy is related to reduced arterial function 20 years later. These data should not alter current recommendations in favour of breast feeding, which has several benefits for infant health. Further work is needed, however, to explore the optimal duration of breast feeding in relation to cardiovascular outcomes.

A Precise Calibration Technique for Measuring High Gas Temperatures

NASA Technical Reports Server (NTRS)

Gokoglu, Suleyman A.; Schultz, Donald F.

2000-01-01

A technique was developed for direct measurement of gas temperatures in the range of 2050 K 2700 K with improved accuracy and reproducibility. The technique utilized the low-emittance of certain fibrous materials, and the uncertainty of the technique was United by the uncertainty in the melting points of the materials, i.e., +/-15 K. The materials were pure, thin, metal-oxide fibers whose diameters varied from 60 microns to 400 microns in the experiments. The sharp increase in the emittance of the fibers upon melting was utilized as indication of reaching a known gas temperature. The accuracy of the technique was confirmed by both calculated low emittance values of transparent fibers, of order 0.01, up to a few degrees below their melting point and by the fiber-diameter independence of the results. This melting-point temperature was approached by increments not larger than 4 K, which was accomplished by controlled increases of reactant flow rates in hydrogen-air and/or hydrogen-oxygen flames. As examples of the applications of the technique, the gas-temperature measurements were used: (a) for assessing the uncertainty in inferring gas temperatures from thermocouple measurements, and (b) for calibrating an IR camera to measure gas temperatures. The technique offers an excellent calibration reference for other gas-temperature measurement methods to improve their accuracy and reliably extending their temperature range of applicability.

A Precise Calibration Technique for Measuring High Gas Temperatures

NASA Technical Reports Server (NTRS)

Gokoglu, Suleyman A.; Schultz, Donald F.

1999-01-01

A technique was developed for direct measurement of gas temperatures in the range of 2050 K - 2700 K with improved accuracy and reproducibility. The technique utilized the low-emittance of certain fibrous Materials, and the uncertainty of the technique was limited by the uncertainty in the melting points of the materials, i.e., +/- 15 K. The materials were pure, thin, metal-oxide fibers whose diameters varied from 60 mm to 400 mm in the experiments. The sharp increase in the emittance of the fibers upon melting was utilized as indication of reaching a known gas temperature. The accuracy of the technique was confirmed by both calculated low emittance values of transparent fibers, of order 0.01, up to a few degrees below their melting point and by the fiber-diameter independence of the results. This melting-point temperature was approached by increments not larger than 4 K, which was accomplished by controlled increases of reactant flow rates in hydrogen-air and/or hydrogen- oxygen flames. As examples of the applications of the technique, the gas-temperature measurements were used (a) for assessing the uncertainty in infering gas temperatures from thermocouple measurements, and (b) for calibrating an IR camera to measure gas temperatures. The technique offers an excellent calibration reference for other gas-temperature measurement methods to improve their accuracy and reliably extending their temperature range of applicability.

Visualization of gas dissolution following upward gas migration in porous media: Technique and implications for stray gas

NASA Astrophysics Data System (ADS)

Van De Ven, C. J. C.; Mumford, Kevin G.

2018-05-01

The study of gas-water mass transfer in porous media is important in many applications, including unconventional resource extraction, carbon storage, deep geological waste storage, and remediation of contaminated groundwater, all of which rely on an understanding of the fate and transport of free and dissolved gas. The novel visual technique developed in this study provided both quantitative and qualitative observations of gas-water mass transfer. Findings included interaction between free gas architecture and dissolved plume migration, plume geometry and longevity. The technique was applied to the injection of CO2 in source patterns expected for stray gas originating from oil and gas operations to measure dissolved phase concentrations of CO2 at high spatial and temporal resolutions. The data set is the first of its kind to provide high resolution quantification of gas-water dissolution, and will facilitate an improved understanding of the fundamental processes of gas movement and fate in these complex systems.

Effects of intravesical hydrostatic pressure and volume on the distensibility of the canine prostatic portion of the urethra.

PubMed

Johnston, G R; Feeney, D A; Osborne, C A; Johnston, S D; Smith, F O; Jessen, C R

1985-03-01

Positive-contrast retrograde urethrocystograms were obtained serially on 12 male dogs weighing 11.4 to 23.2 kg before, during, and after the injection of contrast medium until the urinary bladder neck and prostatic and membranous portions of the urethra remained open and distended as viewed by fluoroscopy. Correlations of intravesical volumes and pressures required to achieve maximum distension of the midprostatic portion of the urethra with body weight and surface area were not significant. Because of the variability in intravesical volumes and pressures encountered at maximum distension of the prostatic portion of the urethra, a dose of contrast material expressed relative to body weight or surface area could not be determined for consistently providing maximum distension of the prostatic portion of the urethra.

Comparison of esophagogastric junction distensibility changes during POEM and Heller myotomy using intraoperative FLIP.

PubMed

Teitelbaum, Ezra N; Boris, Lubomyr; Arafat, Fahd O; Nicodème, Frédéric; Lin, Zhiyue; Kahrilas, Peter J; Pandolfino, John E; Soper, Nathaniel J; Hungness, Eric S

2013-12-01

Peroral endoscopic myotomy (POEM) is a novel endoscopic surgical procedure for the treatment of achalasia. The comparative effects of POEM and laparoscopic Heller myotomy (LHM) on esophagogastric junction (EGJ) physiology are unknown. A novel measurement catheter, the functional lumen imaging probe (FLIP), allows for intraoperative evaluation of EGJ compliance by measuring luminal geometry and pressure during volume-controlled distensions. Distensibility index (DI) (defined as the minimum cross-sectional area at the EGJ divided by pressure) was measured with FLIP intraoperatively in patients undergoing LHM and POEM. Separate measurements were taken after each operative step. During LHM, measurements were performed after: (1) induction of anesthesia, (2) insufflation of pneumoperitoneum, (3) hiatal dissection and esophageal mobilization, (4) myotomy, (5) partial fundoplication, and (6) deinsufflation. During POEM, they were performed after: (1) induction of anesthesia, (2) submucosal tunnel creation, and (3) myotomy. Eleven LHM and 14 POEM patients underwent intraoperative FLIP. Baseline DI was similar between groups. LHM resulted in an overall increase in mean DI (pre 1.4 vs. post 7.6 mm(2)/mmHg, using a 40-ml distension volume; p < 0.001). Insufflation of pneumoperitoneum and hiatal dissection did not affect DI. Myotomy caused an increase in DI. Partial fundoplication (6 Toupet, 5 Dor) caused a decrease in DI, and deinsufflation caused an increase in DI. POEM also resulted in an overall increase in mean DI (pre 1.4 vs. post 7.9 mm(2)/mmHg; p < 0.001). Measured individually, both submucosal tunnel creation and myotomy caused increases in DI. When overall changes were compared, there were no differences in the amount of DI increase between LHM and POEM. POEM and LHM result in a similar improvement in EGJ distensibility intraoperatively. Further study is needed to correlate intraoperative FLIP measurements with postoperative symptomatic and physiologic outcomes.

Ethylene Trace-gas Techniques for High-speed Flows

NASA Technical Reports Server (NTRS)

Davis, David O.; Reichert, Bruce A.

1994-01-01

Three applications of the ethylene trace-gas technique to high-speed flows are described: flow-field tracking, air-to-air mixing, and bleed mass-flow measurement. The technique involves injecting a non-reacting gas (ethylene) into the flow field and measuring the concentration distribution in a downstream plane. From the distributions, information about flow development, mixing, and mass-flow rates can be dtermined. The trace-gas apparatus and special considerations for use in high-speed flow are discussed. A description of each application, including uncertainty estimates is followed by a demonstrative example.

Automated measurement of respiratory gas exchange by an inert gas dilution technique

NASA Technical Reports Server (NTRS)

Sawin, C. F.; Rummel, J. A.; Michel, E. L.

1974-01-01

A respiratory gas analyzer (RGA) has been developed wherein a mass spectrometer is the sole transducer required for measurement of respiratory gas exchange. The mass spectrometer maintains all signals in absolute phase relationships, precluding the need to synchronize flow and gas composition as required in other systems. The RGA system was evaluated by comparison with the Douglas bag technique. The RGA system established the feasibility of the inert gas dilution method for measuring breath-by-breath respiratory gas exchange. This breath-by-breath analytical capability permits detailed study of transient respiratory responses to exercise.

Elasticity/distensibility of the ascending aorta: basal conditions and simulated conditions from space flights.

PubMed

Alessandri, N; Tufano, F; Petrassi, M; Alessandri, C; Lanzi, L; Fusco, L; Moscariello, F; De Angelis, C; Tomao, E

2010-05-01

The hysto-morfological composition of the ascending aorta wall gives to the vessel its characteristic elasticity/distensibility, which is deteriorated due to both physiological (age) and pathological events (hypertension, diabetes, dyslipidemia). This contributes to reduce the wall elasticity and to occurrence of cardiovascular events. Thirty young healthy subjects (20 males, 10 females, age <30 yr), were subjected to different postural conditions with and without Lower Body Negative Pressure (LBNP) with conventional procedures, to simulate the microgravity conditions in space flight. During this procedure the cardiovascular parameters and the aorta elasticity were assessed with ecocardiography. The observation of results and statistical comparison showed that despite different hemodynamic conditions and with significant variation of blood pressure related to posture, elasticity/distensibility did not change significantly. The elasticity/distensibility of arterial vessels is the result of two interdependent variables such as blood pressure and systolic and diastolic diameters. While blood pressure and heart rate vary physiologically in relation to posture, the compensation of the vessel diameters modifications maintains the aortic compliance invariate. Therefore, in young healthy people, despite the significant postural and the sudden pressure changes (equivalent to parietal stress) aortic compliance does not alter. This behavior might be related to the low rate of cardiovascular events that are present in healthy people aged under 30 yrs.

Duration of breast feeding and arterial distensibility in early adult life: population based study

PubMed Central

Leeson, C P M; Kattenhorn, M; Deanfield, J E; Lucas, A

2001-01-01

Objectives To test the hypothesis that duration of breast feeding is related to changes in vascular function relevant to the development of cardiovascular disease. Design Population based observational study. Setting Cambridge. Participants 331 adults (171 women, 160 men) aged between 20 and 28 years, born in Cambridge Maternity Hospital. Main outcome measures Distensibility of brachial artery, type and duration of infant feeding, current lipid profile, and other cardiovascular risk factors. Results The longer the period of breast feeding the less distensible the artery wall in early adult life, with no sex differences (regression coefficient = −3.93 μm/month, 95% confidence interval −7.29 to −0.57, P=0.02). However, in those breast fed for less than four months, arterial distensibility was not significantly reduced compared with an exclusively formula fed group. The vascular changes observed were not explained by alterations in plasma cholesterol concentration in adult life. Conclusions Breast feeding in infancy is related to reduced arterial function 20 years later. These data should not alter current recommendations in favour of breast feeding, which has several benefits for infant health. Further work is needed, however, to explore the optimal duration of breast feeding in relation to cardiovascular outcomes. PMID:11250848

Esophagogastric junction distensibility measurements during Heller myotomy and POEM for achalasia predict postoperative symptomatic outcomes

PubMed Central

Teitelbaum, Ezra N.; Soper, Nathaniel J.; Pandolfino, John E.; Kahrilas, Peter J.; Hirano, Ikuo; Boris, Lubomyr; Nicodème, Frédéric; Lin, Zhiyue; Hungness, Eric S.

2015-01-01

Background The functional lumen imaging probe (FLIP) is a novel diagnostic tool that can be used to measure esophagogastric junction (EGJ) distensibility. In this study we performed intraoperative FLIP measurements during laparoscopic Heller myotomy (LHM) and peroral esophageal myotomy (POEM) for treatment of achalasia and evaluated the relationship between EGJ distensibility and postoperative symptoms. Methods Distensibility index (DI) (defined as the minimum cross-sectional area at the EGJ divided by distensive pressure) was measured with FLIP at two time points during LHM and POEM: 1) at baseline after induction of anesthesia, and 2) after operation completion. Results Measurements were performed in 20 patients undergoing LHM and 36 undergoing POEM. Both operations resulted in an increase in DI, although this increase was larger with POEM (7±3.1 vs. 5.1±3.4mm2/mmHg, p<.05). The two patients (both LHM) with the smallest increases in DI (1 and 1.6mm2/mmHg) both had persistent symptoms postoperatively and, overall, LHM patients with larger increases in DI had lower postoperative Eckardt scores. In the POEM group, there was no correlation between change in DI and symptoms; however, all POEM patients experienced an increase in DI of >3mm2/mmHg. When all patients were divided into thirds based on final DI, none in the lowest DI group (<6mm2/mmHg) had symptoms suggestive of reflux (i.e., GerdQ score >7), as compared with 20% in the middle third (6–9mm2/mmHg) and 36% in the highest third (>9mm2/mmHg). Patients within an “ideal” final DI range (4.5–8.5 mm2/mmHg) had optimal symptomatic outcomes (i.e. Eckardt≤1 and GerdQ≤7) in 88% of cases, compared with 47% in those with a final DI above or below that range (p<.05). Conclusions Intraoperative EGJ distensibility measurements with FLIP were predictive of postoperative symptomatic outcomes. These results provide initial evidence that FLIP has the potential to act as a useful calibration tool during operations

Changes in biomechanical properties of glenohumeral joint capsules with adhesive capsulitis by repeated capsule-preserving hydraulic distensions with saline solution and corticosteroid.

PubMed

Koh, Eun S; Chung, Sun G; Kim, Tae Uk; Kim, Hee Chan

2012-12-01

To investigate whether capsule-preserving hydraulic distension with saline solution and corticosteroid for adhesive capsulitis induces biomechanical alterations in glenohumeral joint capsules along with clinical improvements. A case series. University outpatient clinic of physical medicine and rehabilitation. Eighteen patients with unilateral adhesive capsulitis. INTERVENTION AND MAIN OUTCOME MEASUREMENTS: Three hydraulic distensions with saline solution and corticosteroid were performed with 1-month intervals. To avoid rupturing capsules, all distensions were monitored by using real-time pressure-volume curves. Stiffness, maximal volume capacity, and pressure at the maximal volume capacity of the capsule were measured at each intervention. Clinical parameters, such as pain and range of motion, were recorded before, 3 days after, and 1 month after each distension. Stiffness decreased (47.6 ± 27.1 mm Hg/mL to 31.7 ± 18.4 mm Hg/mL to 24.2 ± 14.0 mm Hg/mL, mean SD) and maximal volume capacity increased (18.8 ± 7.3 mL to 20.5 ± 7.5 mL to 24.2 ± 7.0 mL, mean SD) significantly (P = .001 for both) at each repeated hydraulic distension. Pressure at the maximal volume capacity tended to decrease, but the decrements were not statistically significant (P = .662). The clinical parameters were significantly improved throughout and 1 month after the 3 repeat procedures (P < .05 for all). Capsule-preserving hydraulic distension changed the biomechanical properties of the glenohumeral joint capsule, lessening the stiffness and enlarging the volume capacity. These alterations were accompanied by improved range of motion and relief of pain. Repeated capsule-preserving hydraulic distension with saline solution and corticosteroid would be useful to treat adhesive capsulitis and to evaluate the treatment results. Copyright © 2012 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Evaluation of bowel distension and bowel wall visualization according to patient positions during administration of oral contrast media for CT enterography.

PubMed

Lee, Seul Bi; Kim, Seung Ho; Son, Jung Hee; Baik, Ji Yeon

2017-12-01

To compare small bowel distension and bowel wall visualization among three different patients' positions (supine, sitting and right decubitus) during administration of oral contrast media in preparation for CT enterography (CTE). A total of 150 consecutive patients (104 males and 46 females; mean age 34.6 years, range 15-78 years) who were scheduled to undergo CTE were recruited. Patients were randomly allocated into the three position groups during oral contrast media administration, and there were 50 patients in each group. Two blinded radiologists independently scored the luminal distension and visualization of the bowel wall using a continuous 5-point scale (1: worst and 5: best) at the jejunum and ileum. The Mann-Whitney U test was used to evaluate differences between any two groups among the three positions for bowel distension and wall visualization. For ileal distension, the supine and sitting positions performed better than the right decubitus position [for reader 1, mean: 3.4/3.2/2.9 (hereafter, supine/sitting/right decubitus in order), p = 0.002/0.033; for reader 2, 3.3/3.0/2.6, p < 0.001/0.027]. However, there was no significant difference among the three groups for jejunal distension (for reader 1, 2.4/2.3/2.2; for reader 2, 2.4/2.4/2.2, p > 0.05, respectively). For bowel wall visualization, the supine and sitting positions were superior to the right decubitus position for the ileum when scored by one reader (4.0/3.8/3.4, p = 0.001/0.015). Supine and sitting positions during the administration of oral contrast media provided better ileal distension than the right decubitus position in obtaining CTE. Advances in knowledge: The performance of CTE largely depends on adequate luminal distension and wall visualization. As the terminal ileum is the predominant site of small bowel pathology for inflammatory bowel disease, the supine or sitting position would be preferable for patients who are suspected of having small bowel pathology.

Underwater-seal nasogastric tube drainage to relieve gastric distension caused by air swallowing.

PubMed

Solomon, A W; Bramall, J C; Ball, J

2011-02-01

Air swallowing can occur as a psychogenic phenomenon, because of abnormal anatomy, or during non-invasive positive pressure ventilation. Gross distension of the stomach with air can have severe consequences for the respiratory and gastrointestinal systems. We report the case of a 62-year-old man with severe dynamic hyperinflation due to chronic obstructive pulmonary disease, who developed respiratory failure requiring intubation a few hours after radical prostatectomy. Following a percutaneous tracheostomy and weaning of sedation on day six, his abdomen began to enlarge progressively. X-rays revealed massive gastric distension due to air swallowing, which continued despite all efforts to optimise therapy. The use of an underwater seal drainage system on a nasogastric tube improved ventilation and ultimately aided weaning from mechanical support. © 2010 The Authors. Anaesthesia © 2010 The Association of Anaesthetists of Great Britain and Ireland.

Limb venous distension evokes sympathetic activation via stimulation of the limb afferents in humans.

PubMed

Cui, Jian; McQuillan, Patrick M; Blaha, Cheryl; Kunselman, Allen R; Sinoway, Lawrence I

2012-08-15

We have recently shown that a saline infusion in the veins of an arterially occluded human forearm evokes a systemic response with increases in muscle sympathetic nerve activity (MSNA) and blood pressure. In this report, we examined whether this response was a reflex that was due to venous distension. Blood pressure (Finometer), heart rate, and MSNA (microneurography) were assessed in 14 young healthy subjects. In the saline trial (n = 14), 5% forearm volume normal saline was infused in an arterially occluded arm. To block afferents in the limb, 90 mg of lidocaine were added to the same volume of saline in six subjects during a separate visit. To examine whether interstitial perfusion of normal saline alone induced the responses, the same volume of albumin solution (5% concentration) was infused in 11 subjects in separate studies. Lidocaine abolished the MSNA and blood pressure responses seen with saline infusion. Moreover, compared with the saline infusion, an albumin infusion induced a larger (MSNA: Δ14.3 ± 2.7 vs. Δ8.5 ± 1.3 bursts/min, P < 0.01) and more sustained MSNA and blood pressure responses. These data suggest that venous distension activates afferent nerves and evokes a powerful systemic sympathoexcitatory reflex. We posit that the venous distension plays an important role in evoking the autonomic adjustments seen with postural stress in human subjects.

Increased Carotid Intima-Media Thickness and Reduced Distensibility in Human Class III Obesity: Independent and Differential Influences of Adiposity and Blood Pressure on the Vasculature

PubMed Central

Moore, Xiao L.; Michell, Danielle; Lee, Sabrina; Skilton, Michael R.; Nair, Rajesh; Dixon, John B.; Dart, Anthony M.; Chin-Dusting, Jaye

2013-01-01

Carotid intima-media-thickness (cIMT) and carotid distensibility (distensibility), structural and functional properties of carotid arteries respectively, are early markers, as well as strong predictors of cardiovascular disease (CVD). The characteristic of these two parameters in individuals with BMI>40.0 kg/m2 (Class III obesity), however, are largely unknown. The present study was designed to document cIMT and distensibility in this population and to relate these to other factors with established association with CVD in obesity. The study included 96 subjects (65 with BMI>40.0 kg/m2 and 31, age- and gender-matched, with BMI of 18.5 to 30.0 kg/m2). cIMT and distensibility were measured by non-invasive high resolution ultrasonography, circulatory CD133+/KDR+ angiogenic cells and endothelial microparticles (EMP) by flow cytometry, and plasma levels of adipokines, growth factors and cytokines by Luminex immunoassay kits. The study results demonstrated increased cIMT (0.62±0.11 mm vs. 0.54±0.08 mm, P = 0.0002) and reduced distensibility (22.52±10.79 10−3kpa−1 vs. 29.91±12.37 10−3kpa−1, P<0.05) in individuals with BMI>40.0 kg/m2. Both cIMT and distensibility were significantly associated with traditional CVD risk factors, adiposity/adipokines and inflammatory markers but had no association with circulating angiogenic cells. We also demonstrated, for the first time, elevated plasma EMP levels in individuals with BMI>40.0 kg/m2. In conclusion, cIMT is increased and distensibility reduced in Class III obesity with the changes predominantly related to conventional CVD risk factors present in this condition, demonstrating that both cIMT and distensibility remain as CVD markers in Class III obesity. PMID:23342053

Identification of the visceral pain pathway activated by noxious colorectal distension in mice.

PubMed

Kyloh, Melinda; Nicholas, Sarah; Zagorodnyuk, Vladimir P; Brookes, Simon J; Spencer, Nick J

2011-01-01

In patients with irritable bowel syndrome, visceral pain is evoked more readily following distension of the colorectum. However, the identity of extrinsic afferent nerve pathway that detects and transmits visceral pain from the colorectum to the spinal cord is unclear. In this study, we identified which extrinsic nerve pathway(s) underlies nociception from the colorectum to the spinal cord of rodents. Electromyogram recordings were made from the transverse oblique abdominal muscles in anesthetized wild type (C57BL/6) mice and acute noxious intraluminal distension stimuli (100-120 mmHg) were applied to the terminal 15 mm of colorectum to activate visceromotor responses (VMRs). Lesioning the lumbar colonic nerves in vivo had no detectable effect on the VMRs evoked by colorectal distension. Also, lesions applied to the right or left hypogastric nerves failed to reduce VMRs. However, lesions applied to both left and right branches of the rectal nerves abolished VMRs, regardless of whether the lumbar colonic or hypogastric nerves were severed. Electrical stimulation applied to either the lumbar colonic or hypogastric nerves in vivo, failed to elicit a VMR. In contrast, electrical stimulation (2-5 Hz, 0.4 ms, 60 V) applied to the rectum reliably elicited VMRs, which were abolished by selective lesioning of the rectal nerves. DiI retrograde labeling from the colorectum (injection sites 9-15 mm from the anus, measured in unstretched preparations) labeled sensory neurons primarily in dorsal root ganglia (DRG) of the lumbosacral region of the spinal cord (L6-S1). In contrast, injection of DiI into the mid to proximal colon (injection sites 30-75 mm from the anus, measured in unstretched preparations) labeled sensory neurons in DRG primarily of the lower thoracic level (T6-L2) of the spinal cord. The visceral pain pathway activated by acute noxious distension of the terminal 15 mm of mouse colorectum is transmitted predominantly, if not solely, through rectal

Distensibility and Strength of the Pelvic Floor Muscles of Women in the Third Trimester of Pregnancy

PubMed Central

Petricelli, Carla Dellabarba; Resende, Ana Paula Magalhães; Elito Júnior, Julio; Araujo Júnior, Edward; Alexandre, Sandra Maria; Zanetti, Miriam Raquel Diniz; Nakamura, Mary Uchiyama

2014-01-01

Objective. The objective of this study was to compare the role of the pelvic floor muscles between nulliparous and multiparous women in the third trimester of pregnancy, by analyzing the relationship between electrical activity (surface electromyography—EMG), vaginal palpation (modified Oxford scale), and perineal distensibility (Epi-no). Methods. This was an observational cross-sectional study on a sample of 60 healthy pregnant women with no cervical dilation, single fetus, gestational age between 35 and 40 weeks, and maternal age ranging from 15 to 40 years. The methods used were bidigital palpation (modified Oxford scale, graded 0–5), surface EMG (electrical activity during maximal voluntary contraction), and perineal distensibility (Epi-no device). The Pearson correlation coefficient (r) was used to analyze the Epi-no values and the surface EMG findings. The Kruskal-Wallis test was used to compare the median values from surface EMG and Epi-no, using the modified Oxford scale scores. Results. Among the 60 patients included in this study, 30 were nulliparous and 30 multiparous. The average maternal age and gestational age were 26.06 (±5.58) and 36.56 (±1.23), respectively. It was observed that nulliparous women had both higher perineal muscle strength (2.53 ± 0.57 versus 2.06 ± 0.64; P = 0.005) and higher electrical activity (45.35 ± 12.24 μV versus 35.79 ± 11.66 μV; P = 0.003), while among the multiparous women, distensibility was higher (19.39 ± 1.92 versus 18.05 ± 2.14; P = 0.013). We observed that there was no correlation between perineal distensibility and electrical activity during maximal voluntary contraction (r = − 0.193; P = 0.140). However, we found a positive relationship between vaginal palpation and surface electromyography (P = 0.008), but none between Epi-no values (P = 0.785). Conclusion. The electrical activity and muscle strength of the pelvic floor muscles of the multiparous women were damaged, in relation to the

New models of experimental parotitis and parotid gland distension in rats.

PubMed

Okada-Ogawa, Akiko; Shinoda, Masamichi; Honda, Kuniya; Iwata, Koichi

2012-01-01

A significant reduction of the escape threshold to mechanical stimulation of the lateral facial skin was observed bilaterally at days 2 and 3 after unilateral complete Freund's adjuvant (CFA) administration into parotid gland. A slight reduction of mechanical escape threshold was also observed in rats with saline administration. The parotid gland inflammation was verified and quantified by measuring the tissue Evans' blue dye extravasation. The Evans' blue concentration in the parotid gland tissues was significantly greater in the CFA-injected rats than that of the saline-injected rats at 72 h after treatment. On day 10 after CFA administration into the parotid gland, the Evans' blue concentration was recovered to the control level. The administration of capsaicin into the parotid gland did not alter neuronal activities in the transition zone between the trigeminal spinal subnucleus interpolaris and caudalis (Vi/Vc). In contrast, capsaicin administration induced significant increases in the receptive field size and mechanical and cold responses of neurons located in superficial laminae of the C1/C2. The subgroup of C1/C2 neurons responded to mechanical distension of the parotid gland, whereas no Vi/Vc neurons responded to parotid distension.

Evaluation of bowel distension and mural visualisation using neutral oral contrast agents for multidetector-row computed tomography.

PubMed

Lim, Bee Kuan; Bux, Shaik Ismail; Rahmat, Kartini; Lam, Sze Yin; Liew, Yew Wai

2012-11-01

We compared the effectiveness of different types of non-commercial neutral oral contrast agents for bowel distension and mural visualisation in computed tomographic (CT) enterography. 90 consecutive patients from a group of 108 were randomly assigned to receive water (n = 30), 3.8% milk (n = 30) or 0.1% gastrografin (n = 30) as oral contrast agent. The results were independently reviewed by two radiologists who were blinded to the contrast agents used. The degree of bowel distension was qualitatively scored on a four-point scale. The discrimination of bowel loops, mural visualisation and visualisation of mucosal folds were evaluated on a 'yes' or 'no' basis. Side effects of the various agents were also recorded. 3.8% milk was significantly superior to water for bowel distension (jejunum, ileum and terminal ileum), discrimination of bowel loops (jejunum and ileum), mural visualisation and visualisation of mucosal folds (ileum and terminal ileum). It was also significantly superior to 0.1% gastrografin for bowel distension, discrimination of bowel loops, mural visualisation and visualisation of mucosal folds (jejunum, ileum and terminal ileum). However, 10% of patients who received 3.8% milk reported immediate post-test diarrhoea. No side effects were documented for patients who received water and 0.1% gastrografin. 3.8% milk is an effective and superior neutral oral contrast agent for the assessment of the jejunum, ileum and terminal ileum in CT enterography. However, further studies are needed to explore other suitable oral contrast agents for CT enterography in lactose- or cow's milk-intolerant patients.

Reduced carotid baroreceptor distensibility-induced baroreflex resetting contributes to impairment of sodium regulation in rats fed a high-fat diet.

PubMed

Abe, Chikara; Nagai, Yuko; Yamaguchi, Aoi; Aoki, Hitomi; Shimizu, Shuji; Akiyama, Tsuyoshi; Kawada, Toru; Sugimachi, Masaru; Morita, Hironobu

2015-04-15

Decreased carotid arterial compliance has been reported in obese subjects and animals. Carotid baroreceptors are located at the bifurcation of the common carotid artery, and respond to distension of the arterial wall, suggesting that higher pressure is required to obtain the same distension in obese subjects and animals. A hyperosmotic NaCl solution induces circulatory volume expansion and arterial pressure (AP) increase, which reflexively augment renal excretion. Thus, we hypothesized that sodium regulation via the baroreflex might be impaired in response to chronic hyperosmotic NaCl infusion in rats fed a high-fat diet. To examine this hypothesis, we used rats fed a high-fat (Fat) or normal (NFD) diet, and measured mean AP, water and sodium balance, and renal function in response to chronic infusion of hyperosmotic NaCl solution via a venous catheter. Furthermore, we examined arterial baroreflex characteristics with static open-loop analysis and distensibility of the common carotid artery. Significant positive water and sodium balance was observed on the 1st day of 9% NaCl infusion; however, this disappeared by the 2nd day in Fat rats. Mean AP was significantly higher during 9% NaCl infusion in Fat rats compared with NFD rats. In the open-loop analysis of carotid sinus baroreflex, a rightward shift of the neural arc was observed in Fat rats compared with NFD rats. Furthermore, distensibility of the common carotid artery was significantly reduced in Fat rats. These results indicate that a reduced baroreceptor distensibility-induced rightward shift of the neural arc might contribute to impairment of sodium regulation in Fat rats. Copyright © 2015 the American Physiological Society.

Response of the upper esophageal sphincter to esophageal distension is affected by posture, velocity, volume, and composition of the infusate.

PubMed

Babaei, Arash; Dua, Kulwinder; Naini, Sohrab Rahimi; Lee, Justin; Katib, Omar; Yan, Ke; Hoffmann, Raymond; Shaker, Reza

2012-04-01

Studies of the pressure response of the upper esophageal sphincter (UES) to simulated or spontaneous gastroesophageal reflux have shown conflicting results. These discrepancies could result from uncontrolled influence of variables such as posture, volume, and velocity of distension. We characterized in humans the effects of these variables on UES pressure response to esophageal distension. We studied 12 healthy volunteers (average, 27 ± 5 years old; 6 male) using concurrent esophageal infusion and high-resolution manometry to determine UES, lower esophageal sphincter, and intraesophageal pressure values. Reflux events were simulated by distal esophageal injections of room temperature air and water (5, 10, 20, and 50 mL) in individuals in 3 positions (upright, supine, and semisupine). Frequencies of various UES responses were compared using χ(2) analysis. Multinomial logistical regression analysis was used to identify factors that determine the UES response. UES contraction and relaxation were the overriding responses to esophageal water and air distension, respectively, in a volume-dependent fashion (P < .001). Water-induced UES contraction and air-induced UES relaxation were the predominant responses among individuals in supine and upright positions, respectively (P < .001). The prevalence of their respective predominant response significantly decreased in the opposite position. Proximal esophageal dp/dt significantly and independently differentiated the UES response to infusion with water or air. The UES response to esophageal distension is affected by combined effects of posture (spatial orientation of the esophagus), physical properties, and volume of refluxate, as well as the magnitude and rate of increase in intraesophageal pressure. The UES response to esophageal distension can be predicted using a model that incorporates these factors. Copyright © 2012 AGA Institute. Published by Elsevier Inc. All rights reserved.

Ultrasonographic evaluation of abdominal distension in 52 camels (Camelus dromedarius).

PubMed

Tharwat, Mohamed; Al-Sobayil, Fahd; Ali, Ahmed; Buczinski, Sébastien

2012-08-01

The purpose of this study was to assess the diagnostic value of ultrasonography in the evaluation of abdominal distension in 52 camels (Camelus dromedarius). The conditions included trypanosomiasis (n=35), intestinal obstruction (n=12) and ruptured urinary bladder (n=5). Fifteen clinically normal camels were included as controls. Transabdominal and transrectal ultrasonography was carried out on all camels. In animals with trypanosomiasis, ultrasonographic findings included accumulation of massive amounts of hypoechoic abdominal fluids where liver, intestine, kidney, spleen and urinary bladder were imaged floating. Except in two cases of bile duct calcification and one of hepatic abscessation, no detectable abnormal sonographic lesions were detected while imaging the hepatic and renal parenchyma, and the heart and its valves and major blood vessels. In camels with intestinal obstruction, ultrasonographic findings included distended intestinal loops with markedly reduced or absent motility. In one camel, the intestinal lumen contained localised hyperechoic material that was consistent with a foreign body. Hypoechoic fluid with or without fibrin was seen between intestinal loops. In camels with ruptured urinary bladder, ultrasonographic findings included collapsed and perforated bladder, echogenic blood clots within the urinary bladder and peritoneal cavity, increased thickness of the bladder wall, floating intestines in hypoechogenic fluid and echogenic calculi within the urethra. Ultrasonography was considered a useful tool for the evaluation of dromedary camels with abdominal distension. Copyright © 2011 Elsevier Ltd. All rights reserved.

Measurement of esophago-gastric junction cross-sectional area and distensibility by an endolumenal functional lumen imaging probe for the diagnosis of gastro-esophageal reflux disease.

PubMed

Tucker, E; Sweis, R; Anggiansah, A; Wong, T; Telakis, E; Knowles, K; Wright, J; Fox, M

2013-11-01

Measurement of esophago-gastric junction (EGJ) cross-sectional area (CSA) and distensibility by an Endolumenal Functional Lumen Imaging Probe (EndoFLIP®) may distinguish between gastro-esophageal reflux disease (GERD) patients and healthy volunteers (HV). We aimed to assess the agreement of EndoFLIP® measurements with clinical and physiologic diagnosis of GERD. Twenty-one HV and 18 patients with typical GERD symptoms were studied. After gastroscopy, EGJ CSA, and distensibility were measured by EndoFLIP®. Forty-eight hour esophageal pH monitoring was then performed by a wireless system. The ability of EndoFLIP® to discriminate GERD patient and HVs was assessed. Planned secondary analysis then assessed whether EGJ CSA and distensibility were increased in individuals with pathologic acid exposure. Healthy volunteers were younger and had lower body mass index (BMI; both p < 0.001). Pathologic acid exposure was present in 3/21 (14%) HVs and 9/18 (50%) patients (p = 0.126). At 30 mL EndoFLIP® bag volume, EGJ CSA was higher (p = 0.058) and EGJ distensibility was lower (p = 0.020) in HVs than patients. Secondary analysis showed that EGJ measurements were similar in participants with and without pathologic acid exposure (CSA 98 mm² vs 107 mm²; p = 0.789, distensibility; p = 0.704). An inverse association between BMI and CSA (R² = 0.2758, p = 0.001) and distensibility (R² = 0.2005, p = 0.005) was present. Endolumenal Functional Lumen Imaging Probe is not useful for GERD diagnosis because EGJ CSA and distensibility do not distinguish between HVs and GERD patients defined by clinical presentation or pH measurement. This unexpected result may be due to an important, confounding interaction of obesity. © 2013 John Wiley & Sons Ltd.

The electromyographic activity of the external and internal urethral sphincters and urinary bladder on vaginal distension and its role in preventing vaginal soiling with urine during sexual intercourse.

PubMed

Shafik, Ahmed; Shafik, Ali A; Shafik, Ismail A; El Sibai, Olfat

2008-03-01

We investigated the hypothesis that external (EUS) and internal (IUS) urethral sphincters and urinary bladder (UB) respond to penile thrusting (PT) of vagina in a way that prevents urinary leakage during coitus. Vaginal condom was inflated with air in increments of 50-300 ml and EMG of EUS and IUS and vaginal pressure were recorded; test was repeated after anesthetization of vagina, UB, EUS, and IUS. Vaginal distension effected reduction of vesical pressure but increase of IUS EMG until the 150 ml distension was reached, beyond which more vaginal distension caused no further effect; EUS EMG showed no response. Vaginal distension while vagina, UB, EUS, and IUS had been separately anesthetized, produced no change. Vaginal balloon distension appears to effect vesical relaxation and increased IUS tone. This seems to provide a mechanism to avoid urine leakage during coitus and to occur through a reflex we term 'vagino-urethrovesical reflex'.

Demonstration of landfill gas enhancement techniques in landfill simulators

NASA Astrophysics Data System (ADS)

Walsh, J. J.; Vogt, W. G.

1982-02-01

Various techniques to enhance gas production in sanitary landfills were applied to landfill simulators. These techniques include (1) accelerated moisture addition, (2) leachate recycling, (3) buffer addition, (4) nutrient addition, and (5) combinations of the above. Results are compiled through on-going operation and monitoring of sixteen landfill simulators. These test cells contain about 380 kg of municipal solid waste. Quantities of buffer and nutrient materials were placed in selected cells at the time of loading. Water is added to all test cells on a monthly basis; leachate is withdrawn from all cells (and recycled on selected cells) also on a monthly basis. Daily monitoring of gas volumes and refuse temperatures is performed. Gas and leachate samples are collected and analyzed on a monthly basis. Leachate and gas quality and quantity reslts are presented for the first 18 months of operation.

The participation of the nitrergic pathway in increased rate of transitory relaxation of lower esophageal sphincter induced by rectal distension in dogs.

PubMed

Palheta, Michel Santos; Graça, José Ronaldo Vasconcelos da; Santos, Armênio Aguiar dos; Lopes, Liziane Hermógenes; Palheta Júnior, Raimundo Campos; Nobre E Souza, Miguel Ângelo

2014-01-01

The rectal distension in dogs increases the rate of transitory lower esophageal sphincter relaxation considered the main factor causing gastroesophageal reflux. The aim of this study was evaluate the participation of the nitrergic pathway in the increased transitory lower esophageal sphincter relaxation rate induced by rectal distension in anesthetized dogs. Male mongrel dogs (n = 21), weighing 10-15 kg, were fasted for 12 hours, with water ad libitum. Thereafter, they were anesthetized (ketamine 10 mg.Kg-1 + xylazine 20 mg.Kg-1), so as to carry out the esophageal motility evaluation protocol during 120 min. After a 30-minute basal period, the animals were randomly intravenous treated whith: saline solution 0.15M (1ml.Kg-1), L-NAME (3 mg.Kg-1), L-NAME (3 mg.Kg-1) + L-Arginine (200 mg.Kg-1), glibenclamide (1 mg.Kg-1) or methylene blue (3 mg.Kg-1). Forty-five min after these pre-treatments, the rectum was distended (rectal distension, 5 mL.Kg-1) or not (control) with a latex balloon, with changes in the esophageal motility recorded over 45 min. Data were analyzed using ANOVA followed by Student Newman-Keuls test. In comparison to the respective control group, rectal distension induces an increase in transitory lower esophageal sphincter relaxation. Pre-treatment with L-NAME or methylene blue prevents (P<0.05) this phenomenon, which is reversible by L-Arginine plus L-NAME. However, pretreating with glibenclamide failed to abolish this process. Therefore, these experiments suggested, that rectal distension increases transitory lower esophageal sphincter relaxation in dogs via through nitrergic pathways.

Effect of personalized external aortic root support on aortic root motion and distension in Marfan syndrome patients.

PubMed

Izgi, Cemil; Nyktari, Evangelia; Alpendurada, Francisco; Bruengger, Annina Studer; Pepper, John; Treasure, Tom; Mohiaddin, Raad

2015-10-15

Personalized external aortic root support (PEARS) is a novel surgical approach with the aim of stabilizing the aortic root size and decreasing risk of dissection in Marfan syndrome patients. A bespoke polymer mesh tailored to each patient's individual aorta shape is produced by modeling and then surgically implanted. The aim of this study is to assess the mechanical effects of PEARS on the aortic root systolic downward motion (an important determinant of aortic wall stress), aortic root distension and on the left ventricle (LV). A cohort of 27 Marfan patients had a prophylactic PEARS surgery between 2004 and 2012 with 24 having preoperative and follow-up cardiovascular magnetic resonance imaging studies. Systolic downward aortic root motion, aortic root distension, LV volumes/mass and mitral annular systolic excursion before the operation and in the latest follow-up were measured randomly and blinded. After a median follow-up of 50.5 (IQR 25.5-72) months following implantation of PEARS, systolic downward motion of aortic root was significantly decreased (12.6±3.6mm pre-operation vs 7.9±2.9mm latest follow-up, p<0.00001). There was a tendency for a decrease in systolic aortic root distension but this was not significant (median 4.5% vs 2%, p=0.35). There was no significant change in LV volumes, ejection fraction, mass and mitral annular systolic excursion in follow-up. PEARS surgery decreases systolic downward aortic root motion which is an important determinant of longitudinal aortic wall stress. Aortic wall distension and Windkessel function are not significantly impaired in the follow-up after implantation of the mesh which is also supported by the lack of deterioration of LV volumes or mass. Crown Copyright © 2015. Published by Elsevier Ireland Ltd. All rights reserved.

Uncertainty in anticipation of uncomfortable rectal distension is modulated by the autonomic nervous system--a fMRI study in healthy volunteers.

PubMed

Rubio, Amandine; Van Oudenhove, Lukas; Pellissier, Sonia; Ly, Huynh Giao; Dupont, Patrick; Lafaye de Micheaux, Hugo; Tack, Jan; Dantzer, Cécile; Delon-Martin, Chantal; Bonaz, Bruno

2015-02-15

The human brain responds both before and during the application of aversive stimuli. Anticipation allows the organism to prepare its nociceptive system to respond adequately to the subsequent stimulus. The context in which an uncomfortable stimulus is experienced may also influence neural processing. Uncertainty of occurrence, timing and intensity of an aversive event may lead to increased anticipatory anxiety, fear, physiological arousal and sensory perception. We aimed to identify, in healthy volunteers, the effects of uncertainty in the anticipation of uncomfortable rectal distension, and the impact of the autonomic nervous system (ANS) activity and anxiety-related psychological variables on neural mechanisms of anticipation of rectal distension using fMRI. Barostat-controlled uncomfortable rectal distensions were preceded by cued uncertain or certain anticipation in 15 healthy volunteers in a fMRI protocol at 3T. Electrocardiographic data were concurrently registered by MR scanner. The low frequency (LF)-component of the heart rate variability (HRV) time-series was extracted and inserted as a regressor in the fMRI model ('LF-HRV model'). The impact of ANS activity was analyzed by comparing the fMRI signal in the 'standard model' and in the 'LF-HRV model' across the different anticipation and distension conditions. The scores of the psychological questionnaires and the rating of perceived anticipatory anxiety were included as covariates in the fMRI data analysis. Our experiments led to the following key findings: 1) the subgenual anterior cingulate cortex (sgACC) is the only activation site that relates to uncertainty in healthy volunteers and is directly correlated to individual questionnaire score for pain-related anxiety; 2) uncertain anticipation of rectal distension involved several relevant brain regions, namely activation of sgACC and medial prefrontal cortex and deactivation of amygdala, insula, thalamus, secondary somatosensory cortex, supplementary

Mechanical characteristics of distension-evoked peristaltic contractions in the esophagus of systemic sclerosis patients.

PubMed

Gregersen, Hans; Villadsen, Gerda E; Liao, Donghua

2011-12-01

Systemic sclerosis (SS) patients with severe esophageal affection have impaired peristalsis. However, motor function evaluated in vivo by manometry and fluoroscopy does not provide detailed information about the individual contraction cycles. To apply, for the first time in gastrointestinal (GI) patients, a method and principles modified from cardiac research to study esophageal muscle behavior in SS patients. Muscle contraction cycles were analyzed using pressure-cross-sectional area (P-CSA) loops during distension pressure up to 5 kPa. The probe with bag and electrodes for CSA measurements was positioned 7 and 15 cm above the lower esophageal sphincter (LES) in eleven healthy volunteers and eleven SS patients. The P-CSA, the wall tension, Δtension (afterload tension - preload tension), contraction velocity, work output (area of the tension-CSA loops), and power output (preload tension × CSA rate) were analyzed. The P-CSA loops consisted of phases with relaxation and contraction behavior. The tension-stretch ratio loops in patients were shifted to the left at both distension sites, indicative of a stiffer wall in patients. Lower contraction amplitudes and smaller P-CSA loops were observed for the SS patients. The work output, power output, Δtension, and contraction velocity were lower in patients (P < 0.001). Association was found between disease duration and the work output, Δtension, and velocity at pressure steps higher than 3 kPa (P < 0.05). Distension-evoked esophageal contraction can be studied in vivo and analyzed with advanced methods. Increased esophageal stiffness and impaired muscle function that depended on disease duration were observed for SS patients. The analysis may be useful for characterization of other diseases affecting GI function.

Evaluation of pressor and visceromotor reflex responses to bladder distension in urethane anesthetized rats.

PubMed

Blatt, Lauren K; Lashinger, Erin S R; Laping, Nicholas J; Su, Xin

2009-01-01

We tested cardiovascular and visceromotor reflex (VMR) responses to urinary bladder distension (UBD) in urethane anesthetized rats to see if it can replicate the response pattern and the inhibition of bladder nociceptive transmission by analgesics seen in isoflurane anesthetized animals. Female Sprague-Dawley rats under 3% isoflurane anesthesia were acutely instrumented with jugular venous, carotid arterial, and bladder cannulas for drug administration, blood pressure (BP) measurement, and bladder distension, respectively. Needle electrodes were placed directly into the abdominal musculature to measure myoelectrical activity subsequent to phasic UBD (30 sec in 3 min intervals). A cardiovascular response (pressor) and a VMR response (a contraction of abdominal and hind limb musculature) to UBD were evaluated in urethane (1.2 g/kg, i.v.) or isoflurane (1%) anesthetized rats. Pressor and VMR responses to noxious UBD (60 mmHg) were generated under both anesthesics. The thresholds of stimulus response functions for both pressor and VMR responses were not affected by either anesthesics. However, the magnitude of the maximal pressor response was significantly reduced in urethane anesthesia. The analgesics, morphine, and mexiletine, significantly inhibited the VMR response to noxious UBD under both anesthetics, but the intensities of the inhibition from both analgesics under urethane anesthesia were much lower than under isoflurane anesthesia (ID50: 2.07 mg/kg vs. 0.88 mg/kg for morphine, >10 mg/kg vs. 0.47 mg/kg for mexiletine). The rat urinary bladder distension model in urethane anesthetized rats demonstrates a blunted maximal pressor response and a reduced inhibition of visceral nociceptive transmission by analgesics. Neurourol. Urodynam. 28:442-446, 2009. (c) 2008 Wiley-Liss, Inc.

Excessive coupling of the salience network with intrinsic neurocognitive brain networks during rectal distension in adolescents with irritable bowel syndrome: a preliminary report

PubMed Central

Liu, Xiaolin; Silverman, Alan; Kern, Mark; Ward, B. Douglas; Li, Shi-Jiang; Shaker, Reza; Sood, Manu R.

2015-01-01

Background The neural network mechanisms underlying visceral hypersensitivity in irritable bowel syndrome (IBS) are incompletely understood. It has been proposed that an intrinsic salience network plays an important role in chronic pain and IBS symptoms. Using neuroimaging, we examined brain responses to rectal distension in adolescent IBS patients, focusing on determining the alteration of salience network integrity in IBS and its functional implications in current theoretical frameworks. We hypothesized that (1) brain responses to visceral stimulation in adolescents are similar to those in adults, and (2) IBS is associated with an altered salience network interaction with other neurocognitive networks, particularly the default mode network (DMN) and executive control network (ECN), as predicted by the theoretical models. Methods IBS patients and controls received subliminal and liminal rectal distension during imaging. Stimulus-induced brain activations were determined. Salience network integrity was evaluated by functional connectivity of its seed regions activated by rectal distension in the insular and cingulate cortices. Key Results Compared with controls, IBS patients demonstrated greater activation to rectal distension in neural structures of the homeostatic afferent and emotional arousal networks, especially the anterior cingulate and insular cortices. Greater brain responses to liminal vs. subliminal distension were observed in both groups. Particularly, IBS is uniquely associated with an excessive coupling of the salience network with the DMN and ECN in their key frontal and parietal node areas. Conclusions & Inferences Our study provided consistent evidence supporting the theoretical predictions of altered salience network functioning as a neuropathological mechanism of IBS symptoms. PMID:26467966

Multislice computed tomography with colon water distension (MSCT-c) in the study of intestinal and ureteral endometriosis.

PubMed

Iosca, Simona; Lumia, Domenico; Bracchi, Elena; Duka, Ejona; De Bon, Monica; Lekaj, Manjola; Uccella, Stefano; Ghezzi, Fabio; Fugazzola, Carlo

2013-01-01

This study evaluates retrospectively the accuracy and reproducibility of multislice computed tomography with colon water distension (MSCT-c) in diagnosing bowel (BE) and ureteral (UE) endometriosis. Sixty-four patients underwent MSCT-c and videolaparoscopic surgery. Two radiologists reviewed MSCT-c examinations: sensitivity and specificity were calculated, considering histological exam as reference standard. In the BE cases, the degree of bowel wall infiltration was also assessed. Sensitivity and specificity for both readers were 100% and 97.6% for BE and 72.2% and 100% for UE; the interobserver agreement was excellent. The degree of bowel wall involvement was correctly defined in 90.9% of cases. MSCT-c is an accurate and reproducible technique but-considering the age of the patients-delivers a nonnegligible radiation dose. © 2013 Elsevier Inc. All rights reserved.

New technique for calibrating hydrocarbon gas flowmeters

NASA Technical Reports Server (NTRS)

Singh, J. J.; Puster, R. L.

1984-01-01

A technique for measuring calibration correction factors for hydrocarbon mass flowmeters is described. It is based on the Nernst theorem for matching the partial pressure of oxygen in the combustion products of the test hydrocarbon, burned in oxygen-enriched air, with that in normal air. It is applied to a widely used type of commercial thermal mass flowmeter for a number of hydrocarbons. The calibration correction factors measured using this technique are in good agreement with the values obtained by other independent procedures. The technique is successfully applied to the measurement of differences as low as one percent of the effective hydrocarbon content of the natural gas test samples.

Sympathetic and cardiovascular responses to venous distension in an occluded limb.

PubMed

Cui, Jian; Leuenberger, Urs A; Gao, Zhaohui; Sinoway, Lawrence I

2011-12-01

We recently showed that a fixed volume (i.e., 40 ml) of saline infused into the venous circulation of an arterially occluded vascular bed increases muscle sympathetic nerve activity (MSNA) and blood pressure. In the present report, we hypothesized that the volume and rate of infusion would influence the magnitude of the sympathetic response. Blood pressure, heart rate, and MSNA were assessed in 13 young healthy subjects during forearm saline infusions (arrested circulation). The effects of different volumes of saline (i.e., 2%, 3%, 4%, or 5% forearm volume at 30 ml/min) and different rates of infusion (i.e., 5% forearm volume at 10, 20, or 30 ml/min) were evaluated. MSNA and blood pressure responses were linked with the infusion volume. Infusion of 5% of forearm volume evoked greater MSNA responses than did infusion of 2% of forearm volume (Δ11.6 ± 1.9 vs. Δ3.1 ± 1.8 bursts/min and Δ332 ± 105 vs. Δ38 ± 32 units/min, all P < 0.05). Moreover, greater MSNA responses were evoked by saline infusion at 30 ml/min than 10 ml/min (P < 0.05). Sonographic measurements confirmed that the saline infusions induced forearm venous distension. The results suggest that volume and rate of saline infusion are important factors in evoking sympathetic activation. We postulate that venous distension contributes to cardiovascular autonomic adjustment in humans.

Accuracy of vertical radial plume mapping technique in measuring lagoon gas emissions.

PubMed

Viguria, Maialen; Ro, Kyoung S; Stone, Kenneth C; Johnson, Melvin H

2015-04-01

Recently, the U.S. Environmental Protection Agency (EPA) posted a ground-based optical remote sensing method on its Web site called Other Test Method (OTM) 10 for measuring fugitive gas emission flux from area sources such as closed landfills. The OTM 10 utilizes the vertical radial plume mapping (VRPM) technique to calculate fugitive gas emission mass rates based on measured wind speed profiles and path-integrated gas concentrations (PICs). This study evaluates the accuracy of the VRPM technique in measuring gas emission from animal waste treatment lagoons. A field trial was designed to evaluate the accuracy of the VRPM technique. Control releases of methane (CH4) were made from a 45 m×45 m floating perforated pipe network located on an irrigation pond that resembled typical treatment lagoon environments. The accuracy of the VRPM technique was expressed by the ratio of the calculated emission rates (QVRPM) to actual emission rates (Q). Under an ideal condition of having mean wind directions mostly normal to a downwind vertical plane, the average VRPM accuracy was 0.77±0.32. However, when mean wind direction was mostly not normal to the downwind vertical plane, the emission plume was not adequately captured resulting in lower accuracies. The accuracies of these nonideal wind conditions could be significantly improved if we relaxed the VRPM wind direction criteria and combined the emission rates determined from two adjacent downwind vertical planes surrounding the lagoon. With this modification, the VRPM accuracy improved to 0.97±0.44, whereas the number of valid data sets also increased from 113 to 186. The need for developing accurate and feasible measuring techniques for fugitive gas emission from animal waste lagoons is vital for livestock gas inventories and implementation of mitigation strategies. This field lagoon gas emission study demonstrated that the EPA's vertical radial plume mapping (VRPM) technique can be used to accurately measure lagoon gas

Equilibrium gas-oil ratio measurements using a microfluidic technique.

PubMed

Fisher, Robert; Shah, Mohammad Khalid; Eskin, Dmitry; Schmidt, Kurt; Singh, Anil; Molla, Shahnawaz; Mostowfi, Farshid

2013-07-07

A method for measuring the equilibrium GOR (gas-oil ratio) of reservoir fluids using microfluidic technology is developed. Live crude oils (crude oil with dissolved gas) are injected into a long serpentine microchannel at reservoir pressure. The fluid forms a segmented flow as it travels through the channel. Gas and liquid phases are produced from the exit port of the channel that is maintained at atmospheric conditions. The process is analogous to the production of crude oil from a formation. By using compositional analysis and thermodynamic principles of hydrocarbon fluids, we show excellent equilibrium between the produced gas and liquid phases is achieved. The GOR of a reservoir fluid is a key parameter in determining the equation of state of a crude oil. Equations of state that are commonly used in petroleum engineering and reservoir simulations describe the phase behaviour of a fluid at equilibrium state. Therefore, to accurately determine the coefficients of an equation of state, the produced gas and liquid phases have to be as close to the thermodynamic equilibrium as possible. In the examples presented here, the GORs measured with the microfluidic technique agreed with GOR values obtained from conventional methods. Furthermore, when compared to conventional methods, the microfluidic technique was simpler to perform, required less equipment, and yielded better repeatability.

Micro-CT image-derived metrics quantify arterial wall distensibility reduction in a rat model of pulmonary hypertension

NASA Astrophysics Data System (ADS)

Johnson, Roger H.; Karau, Kelly L.; Molthen, Robert C.; Haworth, Steven T.; Dawson, Christopher A.

2000-04-01

We developed methods to quantify arterial structural and mechanical properties in excised rat lungs and applied them to investigate the distensibility decrease accompanying chronic hypoxia-induced pulmonary hypertension. Lungs of control and hypertensive (three weeks 11% O2) animals were excised and a contrast agent introduced before micro-CT imaging with a special purpose scanner. For each lung, four 3D image data sets were obtained, each at a different intra-arterial contrast agent pressure. Vessel segment diameters and lengths were measured at all levels in the arterial tree hierarchy, and these data used to generate features sensitive to distensibility changes. Results indicate that measurements obtained from 3D micro-CT images can be used to quantify vessel biomechanical properties in this rat model of pulmonary hypertension and that distensibility is reduced by exposure to chronic hypoxia. Mechanical properties can be assessed in a localized fashion and quantified in a spatially-resolved way or as a single parameter describing the tree as a whole. Micro-CT is a nondestructive way to rapidly assess structural and mechanical properties of arteries in small animal organs maintained in a physiological state. Quantitative features measured by this method may provide valuable insights into the mechanisms causing the elevated pressures in pulmonary hypertension of differing etiologies and should become increasingly valuable tools in the study of complex phenotypes in small-animal models of important diseases such as hypertension.

Nonmassive acute pulmonary embolism: evaluation of the impact of pulmonary arterial wall distensibility on the assessment of the CT obstruction score.

PubMed

Bigot, Julien; Rémy-Jardin, Martine; Duhamel, Alain; Gorgos, Andréi-Bogdan; Faivre, Jean-Baptiste; Rémy, Jacques

2010-02-01

To evaluate the impact of pulmonary arterial wall distensibility on the assessment of a computed tomography (CT) score in patients with nonmassive pulmonary embolism (PE) (ie, Mastora score). The arterial wall distensibility of five central pulmonary arteries (pulmonary artery trunk, right and left main pulmonary arteries, right and left interlobar pulmonary arteries) was studied on ECG-gated CT angiographic studies of the chest in 15 patients with no pulmonary arterial hypertension (group 1; mean pulmonary artery pressure: 17.2 mm Hg) and 9 patients with nonmassive PE (group 2), using 2D reconstructions at every 10% of the R-R interval. The systolic and diastolic reconstruction time windows of the examined arteries were identical in the 2 groups, obtained at 20% and 80% of the R-R interval, respectively. No statistically significant difference was observed between the mean values of the pulmonary arterial wall distensibility between the 2 groups, varying between 20.5% and 24% in group 1 and between 23.3% and 25.9% in group 2. The coefficients of variation of the average arterial surfaces were found to vary between 4.30% and 6.50% in group 1 and 4.2% and 8.4% in group 2. Except the pulmonary artery trunk in group 2, all the intraclass correlation coefficients were around 0.8 or greater than 0.8, that is the cutoff for good homogeneity of measurements. The pulmonary arterial wall systolic-diastolic distensibility does not interfere with the assessment of a CT obstruction score in the setting of nonmassive PE.

Mechanisms of postprandial abdominal bloating and distension in functional dyspepsia.

PubMed

Burri, Emanuel; Barba, Elizabeth; Huaman, Jose Walter; Cisternas, Daniel; Accarino, Anna; Soldevilla, Alfredo; Malagelada, Juan-R; Azpiroz, Fernando

2014-03-01

Patients with irritable bowel syndrome and abdominal bloating exhibit abnormal responses of the abdominal wall to colonic gas loads. We hypothesised that in patients with postprandial bloating, ingestion of a meal triggers comparable abdominal wall dyssynergia. Our aim was to characterise abdominal accommodation to a meal in patients with postprandial bloating. A test meal (0.8 kcal/ml nutrients plus 27 g/litre polyethylenglycol 4000) was administered at 50 ml/min as long as tolerated in 10 patients with postprandial bloating (fulfilling Rome III criteria for postprandial distress syndrome) and 12 healthy subjects, while electromyographic (EMG) responses of the anterior wall (upper and lower rectus, external and internal oblique via bipolar surface electrodes) and the diaphragm (via six ring electrodes over an oesophageal tube in the hiatus) were measured. Means +/- SD were calculated. Healthy subjects tolerated a meal volume of 913±308 ml; normal abdominal wall accommodation to the meal consisted of diaphragmatic relaxation (EMG activity decreased by 15±6%) and a compensatory contraction (25±9% increase) of the upper abdominal wall muscles (upper rectus and external oblique), with no changes in the lower anterior muscles (lower rectus and internal oblique). Patients tolerated lower volume loads (604±310 ml; p=0.030 vs healthy subjects) and developed a paradoxical response, that is, diaphragmatic contraction (14±3% EMG increment; p<0.01 vs healthy subjects) and upper anterior wall relaxation (9±4% inhibition; p<0.01 vs healthy subjects). In functional dyspepsia, postprandial abdominal distension is produced by an abnormal viscerosomatic response to meal ingestion that alters normal abdominal accommodation.

Mechanisms of repetitive retrograde contractions in response to sustained esophageal distension: a study evaluating patients with postfundoplication dysphagia.

PubMed

Carlson, Dustin A; Kahrilas, Peter J; Ritter, Katherine; Lin, Zhiyue; Pandolfino, John E

2018-03-01

Repetitive retrograde contractions (RRCs) in response to sustained esophageal distension are a distinct contractility pattern observed with functional luminal imaging probe (FLIP) panometry that are common in type III (spastic) achalasia. RRCs are hypothesized to be indicative of either impaired inhibitory innervation or esophageal outflow obstruction. We aimed to apply FLIP panometry to patients with postfundoplication dysphagia (a model of esophageal obstruction) to explore mechanisms behind RRCs. Adult patients with dysphagia after Nissen fundoplication ( n = 32) or type III achalasia ( n = 25) were evaluated with high-resolution manometry (HRM) and upper endoscopy with FLIP. HRM studies were assessed for outflow obstruction and spastic features: premature contractility, hypercontractility, and impaired deglutitive inhibition during multiple-rapid swallows. FLIP studies were analyzed to determine the esophagogastric junction (EGJ)-distensibility index and contractility pattern, including RRCs. Barium esophagram was evaluated when available. RRCs were present in 8/32 (25%) fundoplication and 19/25 (76%) achalasia patients ( P < 0.001). EGJ outflow obstruction was detected in 21 (67%) fundoplication patients by HRM, FLIP, or esophagram [6 (29%) had RRCs]. On HRM, none of the fundoplication patients had premature contractility, whereas 3/4 with defective inhibition on multiple-rapid swallows and 2/4 with hypercontractility had RRCs. Regression analysis demonstrated HRM with spastic features, but not esophageal outflow obstruction, as a predictor for RRCs. RRCs in response to sustained esophageal distension appear to be a manifestation of spastic esophageal motility. Although future study to further clarify the significance of RRCs is needed, RRCs on FLIP panometry should prompt evaluation for a major motor disorder. NEW & NOTEWORTHY Repetitive retrograde contractions (RRCs) are a common response to sustained esophageal distension among spastic achalasia patients

Effects of gastric distension and feeding on cardiovascular variables in the shorthorn sculpin (Myoxocephalus scorpius).

PubMed

Seth, Henrik; Axelsson, Michael

2009-01-01

We have previously shown in rainbow trout (Oncorhynchus mykiss) that gastric distension induces an instantaneous alpha-adrenoceptor-mediated increase in the dorsal aortic blood pressure (P(da)), with no change in cardiac output (CO), gut blood flow (Q(cma)), or heart rate. To investigate if feeding habits affect these patterns and to compare the differences between gastric distension alone and feeding in the same experimental setting, we used the short-horn sculpin (Myoxocephalus scorpius), an inactive ambush predator with a capacity to eat large meals. An inflatable balloon was placed in the stomach of one group while another group was fed fish meat. When distending the stomach with a volume corresponding to a meal of 8-10% body weight, there is a profound and long-lasting increase in systemic (123 +/- 27%) and gastrointestinal (R(cma); 82 +/- 24%) vascular resistance, leading to an increase in P(da) (19%) without any change in CO or Q(cma). After force-feeding, there is a rapid transient increase in R(cma) (24 +/- 4%) and an even larger P(da) response (53%). There is also a subsequent increase in both CO (28 +/- 8%) and Q(cma) (27 +/- 9%) after 30 min. By 15 h, CO and Q(cma) increase further (41 +/- 11 and 63 +/- 14%, respectively), and this increase persists for up to 60 h. The increase in Q(cma) is mediated via both an increase in CO and a shunting of blood from the systemic circulation via a decrease in R(cma) (34 +/- 7%). In conclusion, the response to mechanical distension of the stomach is similar to what we have described in rainbow trout, and the postprandial gastrointestinal hyperemia is most likely chemically induced.

Neural control of ventilation prevents both over-distension and de-recruitment of experimentally injured lungs.

PubMed

Brander, Lukas; Moerer, Onnen; Hedenstierna, Göran; Beck, Jennifer; Takala, Jukka; Slutsky, Arthur S; Sinderby, Christer

2017-03-01

Endogenous pulmonary reflexes may protect the lungs during mechanical ventilation. We aimed to assess integration of continuous neurally adjusted ventilatory assist (cNAVA), delivering assist in proportion to diaphragm's electrical activity during inspiration and expiration, and Hering-Breuer inflation and deflation reflexes on lung recruitment, distension, and aeration before and after acute lung injury (ALI). In 7 anesthetised rabbits with bilateral pneumothoraces, we identified adequate cNAVA level (cNAVA AL ) at the plateau in peak ventilator pressure during titration procedures before (healthy lungs with endotracheal tube, [HL ETT ]) and after ALI (endotracheal tube [ALI ETT ] and during non-invasive ventilation [ALI NIV ]). Following titration, cNAVA AL was maintained for 5min. In 2 rabbits, procedures were repeated after vagotomy (ALI ETT+VAG ). In 3 rabbits delivery of assist was temporarily modulated to provide assist on inspiration only. Computed tomography was performed before intubation, before ALI, during cNAVA titration, and after maintenance at cNAVA AL . During ALI ETT and ALI NIV , normally aerated lung-regions doubled and poorly aerated lung-regions decreased to less than a third (p<0.05) compared to HL ETT ; no over-distension was observed. Tidal volumes were<5ml/kg throughout. Removing assist during expiration resulted in lung de-recruitment during ALI ETT , but not during ALI NIV . During ALI ETT+VAG the expiratory portion of EAdi disappeared, resulting in cyclic lung collapse and recruitment. When using cNAVA in ALI, vagally mediated reflexes regulated lung recruitment preventing both lung over-distension and atelectasis. During non-invasive cNAVA the upper airway muscles play a role in preventing atelectasis. Future studies should be performed to compare these findings with conventional lung-protective approaches. Copyright © 2016 Elsevier B.V. All rights reserved.

Experimental short-duration techniques. [gas turbine engine tests

NASA Technical Reports Server (NTRS)

Dunn, Michael G.

1986-01-01

Short-duration facilities used for gas turbine studies are described. Data recording techniques; and instruments (thin-film heat flux gages, high-frequency response pressure measurements, total temperature probes, measurement of rotor tip speed, active measurement of tip clearance) are presented.

Practical Techniques for Modeling Gas Turbine Engine Performance

NASA Technical Reports Server (NTRS)

Chapman, Jeffryes W.; Lavelle, Thomas M.; Litt, Jonathan S.

2016-01-01

The cost and risk associated with the design and operation of gas turbine engine systems has led to an increasing dependence on mathematical models. In this paper, the fundamentals of engine simulation will be reviewed, an example performance analysis will be performed, and relationships useful for engine control system development will be highlighted. The focus will be on thermodynamic modeling utilizing techniques common in industry, such as: the Brayton cycle, component performance maps, map scaling, and design point criteria generation. In general, these topics will be viewed from the standpoint of an example turbojet engine model; however, demonstrated concepts may be adapted to other gas turbine systems, such as gas generators, marine engines, or high bypass aircraft engines. The purpose of this paper is to provide an example of gas turbine model generation and system performance analysis for educational uses, such as curriculum creation or student reference.

Human Placental Arterial Distensibility, Birth Weight, and Body Size Are Positively Related to Fetal Homocysteine Concentration.

PubMed

D'Souza, Stephen W; Solanky, Nita; Guarino, Jane; Moat, Stuart; Sibley, Colin P; Taggart, Michael; Glazier, Jocelyn D

2017-07-01

Methionine demethylation during metabolism generates homocysteine (Hcy) and its remethylation requires folate and cobalamin. Elevated Hcy concentrations are associated with vascular-related complications of pregnancy, including increased vascular stiffness, predictive of clinical vascular disease. Maternal and fetal total Hcy (tHcy) concentrations are positively related, yet the influence of Hcy on fetoplacental vascular function in normal pregnancy has not been examined. We hypothesized that Hcy alters fetoplacental vascular characteristics with influences on fetal growth outcomes. We investigated (1) placental chorionic plate artery distensibility and neonatal blood pressure in relation to umbilical plasma tHcy; (2) relationships between cord venous (CV) and cord arterial (CA) plasma tHcy, folate, and cobalamin concentrations; and (3) tHcy associations with birth weight and anthropometric measurements of body size as indices of fetal growth in normal pregnancies with appropriate weight-for-gestational age newborns. Maternal plasma tHcy, folate, and cobalamin concentrations were consistent with published data. Placental chorionic plate artery distensibility index (β; measure of vessel stiffness) was inversely related to CA tHcy, yet neonatal blood pressure was not significantly affected. CV and CA tHcy concentrations were positively related and CV tHcy negatively related to CV cobalamin but not folate. CV tHcy concentration positively related to birth weight, corrected birth weight percentile, length, head circumference, and mid-arm circumference of newborns. CV cobalamin was inversely related to fetal growth indices but not to folate concentration. Our study demonstrates a potential relationship between fetal tHcy and placental artery distensibility, placing clinical relevance to cobalamin in influencing Hcy concentration and maintaining low vascular resistance to facilitate nutrient exchange favorable to fetal growth.

Comparison of three types of stress urinary incontinence rat models: electrocauterization, pudendal denervation, and vaginal distension.

PubMed

Hong, Sung-Hoo; Piao, Shuyu; Kim, In Gul; Lee, Ji Young; Cho, Hyuk Jin; Kim, Sae Woong; Hwang, Tae-Kon; Lee, Ji Youl

2013-02-01

To investigate the differences in the histopathologic and functional characteristics of 3 rat models of stress urinary incontinence. A total of 24 female, 10-week-old, Sprague-Dawley rats were randomly divided into 4 groups: normal, electrocauterization, pudendal denervation, and vaginal distension. At 2 weeks after surgery, the leak point pressure was measured to detect urinary leakage. Urethral tissue samples were collected for histological examination. The smooth muscle content in the electrocauterization group was significantly decreased compared with that in all other groups, indicating that electrocauterization caused the most severe injury. A blood vessel marker, von Willebrand factor, was co-stained with α-smooth muscle actin to detect the blood vessel distribution. No significant differences were seen in von Willebrand factor expression among the 4 groups, other than in the electrocauterization group, in which we could hardly observe blood vessel expression. Protein gene product 9.5 staining was used to detect nerve fibers and cells. Protein gene product 9.5 expression was significantly lower in all the treatment groups compared with that in the normal group (P <.05), in particular, in the electrocauterization and pudendal denervation groups (P <.01). The leak point pressure was significantly lower in the electrocauterization (P <.01), pudendal denervation (P <.01), and vaginal distension (P <.05) groups than in the normal group. The vaginal distension model should mainly be used as the myogenic damage stress urinary incontinence animal model; the pudendal denervation model mainly as the neurogenic damage stress urinary incontinence animal model; and the electrocauterization model as the vasculogenic, neurogenic, and myogenic damage animal model. Copyright © 2013. Published by Elsevier Inc.

SU-E-T-129: Are Knowledge-Based Planning Dose Estimates Valid for Distensible Organs?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lalonde, R; Heron, D; Huq, M

2015-06-15

Purpose: Knowledge-based planning programs have become available to assist treatment planning in radiation therapy. Such programs can be used to generate estimated DVHs and planning constraints for organs at risk (OARs), based upon a model generated from previous plans. These estimates are based upon the planning CT scan. However, for distensible OARs like the bladder and rectum, daily variations in volume may make the dose estimates invalid. The purpose of this study is to determine whether knowledge-based DVH dose estimates may be valid for distensible OARs. Methods: The Varian RapidPlan™ knowledge-based planning module was used to generate OAR dose estimatesmore » and planning objectives for 10 prostate cases previously planned with VMAT, and final plans were calculated for each. Five weekly setup CBCT scans of each patient were then downloaded and contoured (assuming no change in size and shape of the target volume), and rectum and bladder DVHs were recalculated for each scan. Dose volumes were then compared at 75, 60,and 40 Gy for the bladder and rectum between the planning scan and the CBCTs. Results: Plan doses and estimates matched well at all dose points., Volumes of the rectum and bladder varied widely between planning CT and the CBCTs, ranging from 0.46 to 2.42 for the bladder and 0.71 to 2.18 for the rectum, causing relative dose volumes to vary between planning CT and CBCT, but absolute dose volumes were more consistent. The overall ratio of CBCT/plan dose volumes was 1.02 ±0.27 for rectum and 0.98 ±0.20 for bladder in these patients. Conclusion: Knowledge-based planning dose volume estimates for distensible OARs are still valid, in absolute volume terms, between treatment planning scans and CBCT’s taken during daily treatment. Further analysis of the data is being undertaken to determine how differences depend upon rectum and bladder filling state. This work has been supported by Varian Medical Systems.« less

Inverse-dispersion technique for assessing lagoon gas emissions

USDA-ARS?s Scientific Manuscript database

Measuring gas emissions from treatment lagoons and storage ponds poses challenging conditions for existing micrometeorological techniques because of non-ideal wind conditions, such as those induced by trees and crops surrounding the lagoons, and lagoons with dimensions too small to establish equilib...

Carotid and Femoral Arterial Wall Distensibility During Long-Duration Spaceflight.

PubMed

Arbeille, Philippe; Provost, Romain; Zuj, Kathryn

2017-10-01

This study aimed to assess changes in common carotid (CA) and superficial femoral (FA) arterial stiffness during long-duration spaceflight. Ultrasound imaging was used to investigate the CA and FA of 10 astronauts preflight (PRE), on flight day 15 (FD15), after 4-5 mo (FD4-5m), and 4 d after return to Earth (R+4). Arterial wall properties were assessed through the calculation of strain, stiffness (β), pressure-strain elastic modulus (Ep), and distensibility (DI). Stiffness indices were assessed for potential correlations to measurements of intima-media thickness (IMT). Significant effects of spaceflight were found for all CA stiffness indices, indicating an increase in arterial stiffness. CA strain was reduced by 34 ± 31% on FD15 and 50 ± 16% on FD4-5m and remained reduced by 42 ± 14% on R+4 with respect to PRE values. On FD4-5m, with respect to PRE values, DI was reduced by 46 ± 25% and β and Ep were increased by 124 ± 95% and 118 ± 92%, respectively. FA arterial stiffness indices appeared to show similar changes; however, a main effect of spaceflight was only found for strain. Correlation analysis showed weak but significant relationships between measurements of CA IMT and arterial stiffness indices, but no relationships were found for FA measurements. The observed change in CA and FA stiffness indices suggest that spaceflight results in an increase in arterial stiffness. That these changes were not strongly related to measurements of IMT suggests the possibility of different mechanisms contributing to the observed results.Arbeille P, Provost R, Zuj K. Carotid and femoral arterial wall distensibility during long-duration spaceflight. Aerosp Med Hum Perform. 2017; 88(10):924-930.

Comparative potency of carbachol, sham feeding, fundic distension and 16,16-dimethyl prostaglandin E2 as stimulants of human gastric bicarbonate secretion.

PubMed

Forssell, H; Lind, T; Olbe, L

1988-09-01

Six healthy subjects in random order underwent gastric bicarbonate secretion investigations, including stimulation with increasing doses of the cholinergic agonist carbachol, sham feeding, fundic distension and gastric instillation of 16,16-dimethyl prostaglandin E2. Bicarbonate secretion was measured by a computer-based system which continuously recorded pH and PCO2 of the effluent in a high-volume gastric perfusion system. The peak 30 min gastric bicarbonate output in response to carbachol, 150 mg subcutaneously, was 114% (P less than 0.05). Vagal stimulation by sham feeding resulted in a corresponding increase of 112% (P less than 0.05), while fundic distension to a volume of 600 ml gave an increase of 114% (P less than 0.05). In comparison, the response to 80 micrograms 16,16-dimethyl prostaglandin E2 was much greater, the peak bicarbonate output being increased by 245% (P less than 0.05). Both sham feeding and fundic distension appear to be either submaximal stimuli of gastric bicarbonate secretion in man or may possess both stimulatory and inhibitory actions.

Characterizing Gas Transport in Wetland Soil-Root Systems with Dissolved Gas Tracer Techniques

NASA Astrophysics Data System (ADS)

Reid, M. C.; Jaffe, P. R.

2016-12-01

Soil fluxes of methane (CH4), nitrous oxide (N2O), and other biogenic gases depend on coupling between microbial and physiochemical processes within soil media. The importance of plant-mediated transport in wetland CH4 emissions is well known, but a generalized understanding of gas transfer between pore water and root aerenchyma, and how this process competes with biogeochemical production/consumption of gases beyond CH4, is incomplete [1]. A lack of experimental approaches to characterize transport processes in complex soil-water-plant systems at field scale has limited efforts to close this knowledge gap. In this presentation we describe dissolved gas tracer techniques to tease apart effects of transport from simultaneous biochemical reaction on trace gas dynamics in soils. We discuss a push-pull test with helium and sulfur hexafluoride gas tracers to quantify in situ root-mediated gas transfer kinetics in a wetland soil [2]. A Damköhler number analysis is introduced to interpret the results and evaluate the balance between biochemical reaction and root-driven gas transfer in controlling the fate of CH4 and N2O in vegetated wetland soils. We conclude with a brief discussion of other problems in soil gas dynamics that can be addressed with gas tracer approaches. [1] Blagodatsky and Smith 2012. Soil physics meets soil biology: Towards better mechanistic prediction of greenhouse gas emissions from soil. Soil Biology and Biochemistry 47, 78-92. [2] Reid et al. 2015. Dissolved gas dynamics in wetland soils: Root-mediated gas transfer kinetics determind via push-pull tracer tests. Water Resour. Res. 51, doi:10.1002/2014WR016803.

Venous distension in the diabetic neuropathic foot (physical sign of arteriovenous shunting).

PubMed Central

Ward, J D; Boulton, A J; Simms, J M; Sandler, D A; Knight, G

1983-01-01

A new physical sign is described in the feet of a group of diabetic patients with ulcerating neuropathic problems, in which major venous distension of the veins on the dorsum of the foot and lower calf is seen. Elevation of the leg is required to an average height of 32.3 cm to cause collapse of these distended veins. It is suggested that this clinical sign indicates the presence of arteriovenous shunting in such neuropathic legs, and as such is a simple and useful measure of this abnormality. Images Figure 1. Figure 2. PMID:6672192

Modeling Gas and Gas Hydrate Accumulation in Marine Sediments Using a K-Nearest Neighbor Machine-Learning Technique

NASA Astrophysics Data System (ADS)

Wood, W. T.; Runyan, T. E.; Palmsten, M.; Dale, J.; Crawford, C.

2016-12-01

Natural Gas (primarily methane) and gas hydrate accumulations require certain bio-geochemical, as well as physical conditions, some of which are poorly sampled and/or poorly understood. We exploit recent advances in the prediction of seafloor porosity and heat flux via machine learning techniques (e.g. Random forests and Bayesian networks) to predict the occurrence of gas and subsequently gas hydrate in marine sediments. The prediction (actually guided interpolation) of key parameters we use in this study is a K-nearest neighbor technique. KNN requires only minimal pre-processing of the data and predictors, and requires minimal run-time input so the results are almost entirely data-driven. Specifically we use new estimates of sedimentation rate and sediment type, along with recently derived compaction modeling to estimate profiles of porosity and age. We combined the compaction with seafloor heat flux to estimate temperature with depth and geologic age, which, with estimates of organic carbon, and models of methanogenesis yield limits on the production of methane. Results include geospatial predictions of gas (and gas hydrate) accumulations, with quantitative estimates of uncertainty. The Generic Earth Modeling System (GEMS) we have developed to derive the machine learning estimates is modular and easily updated with new algorithms or data.

Impact of airway gas exchange on the multiple inert gas elimination technique: theory.

PubMed

Anderson, Joseph C; Hlastala, Michael P

2010-03-01

The multiple inert gas elimination technique (MIGET) provides a method for estimating alveolar gas exchange efficiency. Six soluble inert gases are infused into a peripheral vein. Measurements of these gases in breath, arterial blood, and venous blood are interpreted using a mathematical model of alveolar gas exchange (MIGET model) that neglects airway gas exchange. A mathematical model describing airway and alveolar gas exchange predicts that two of these gases, ether and acetone, exchange primarily within the airways. To determine the effect of airway gas exchange on the MIGET, we selected two additional gases, toluene and m-dichlorobenzene, that have the same blood solubility as ether and acetone and minimize airway gas exchange via their low water solubility. The airway-alveolar gas exchange model simulated the exchange of toluene, m-dichlorobenzene, and the six MIGET gases under multiple conditions of alveolar ventilation-to-perfusion, VA/Q, heterogeneity. We increased the importance of airway gas exchange by changing bronchial blood flow, Qbr. From these simulations, we calculated the excretion and retention of the eight inert gases and divided the results into two groups: (1) the standard MIGET gases which included acetone and ether and (2) the modified MIGET gases which included toluene and m-dichlorobenzene. The MIGET mathematical model predicted distributions of ventilation and perfusion for each grouping of gases and multiple perturbations of VA/Q and Qbr. Using the modified MIGET gases, MIGET predicted a smaller dead space fraction, greater mean VA, greater log(SDVA), and more closely matched the imposed VA distribution than that using the standard MIGET gases. Perfusion distributions were relatively unaffected.

The effect of FAAH, MAGL, and Dual FAAH/MAGL inhibition on inflammatory and colorectal distension-induced visceral pain models in Rodents.

PubMed

Sakin, Y S; Dogrul, A; Ilkaya, F; Seyrek, M; Ulas, U H; Gulsen, M; Bagci, S

2015-07-01

Recent studies showed that the pharmacological inhibition of endocannabinoid degrading enzymes such as fatty acid amide hydrolase (FAAH) and monoacyl glycerol lipase (MAGL) elicit promising analgesic effects in a variety of nociceptive models without serious side effects. However, the full spectrum of activities is not observed upon inhibition of either FAAH or MAGL enzymes alone and thus dual FAAH and MAGL inhibitors have been described. Visceral pain is strongly associated with inflammation and distension of the gut. Thus, we explored the comparable effects of FAAH, MAGL, and dual FAAH/MAGL inhibitors on inflammatory and mechanically evoked visceral pain models. Visceral inflammatory and distension-induced pain were assessed with the 0.6% acetic acid writhing test in mice and colorectal distension (CRD) test in rats, respectively. The selective FAAH inhibitor PF 3845, MAGL inhibitor JZL 184, dual inhibitor JZL 195, and the cannabis analog CP 55,940 were given systemically 30 min prior to nociceptive testing. PF 3845 (5, 10, and 20 mg/kg), JZL 184 (5, 10, and 20 mg/kg), and JZL 195 (5, 10, and 20 mg/kg) elicit dose-dependent antinociceptive in the acetic acid writhing test. In the CRD model, while JZL 195 (5, 10, or 20 mg/kg) and PF3845 (10, 20, and 40 mg/kg) produced dose-dependent antinociceptive effects comparable to those of CP 55,940 (0.1, 0.3, or 1 mg/kg), JZL 184 (10, 20, and 40 mg/kg) alone did not alter the visceromotor response (VMR). The selective FAAH inhibitor and dual FAAH/MAGL inhibitors were effective in both inflammatory and mechanically evoked visceral pain, while the MAGL inhibitor elicited an analgesic effect in inflammatory, but not in distension-induced, visceral pain. © 2015 John Wiley & Sons Ltd.

The effect of incremental distal gastric myotomy lengths on EGJ distensibility during POEM for achalasia

PubMed Central

Teitelbaum, Ezra N.; Sternbach, Joel M.; Khoury, Rym El; Soper, Nathaniel J.; Pandolfino, John E.; Kahrilas, Peter J.; Lin, Zhiyue; Hungness, Eric S.

2015-01-01

Background During peroral esophageal myotomy (POEM) for the treatment of achalasia, the optimal distal gastric myotomy length is unknown. In this study we used a functional lumen imaging probe (FLIP) to intraoperatively measure the effect of variable distal myotomy lengths on esophagogastric junction (EGJ) distensibility. Methods EGJ distensibility index (DI) (minimum cross-sectional area divided by intra-bag pressure) was measured with FLIP after each operative step. Each patient's myotomy was performed in four increments from proximal to distal: 1) an esophageal myotomy (from 6cm proximal to the EGJ, to 1cm proximal to it), 2) a myotomy ablating the lower esophageal sphincter (LES) complex (from 1cm proximal to the EGJ, to 1cm distal to it), 3) an initial gastric extension (from 1cm distal to the EGJ, to 2cm distal), and 4) a final gastric extension (from 2cm distal to the EGJ, to 3cm distal). Results Measurements were performed in 16 achalasia patients during POEM. POEM resulted in an overall increase in DI (pre 1.2 vs. post 7.2 mm2/mmHg, p<.001). Initial creation of the submucosal tunnel resulted in a 3-fold increase in DI (1.2 vs. 3.6 mm2/mmHg, p<.001). When the myotomy was then performed in a stepwise fashion from proximal to distal, the initial esophageal myotomy component had no effect on DI. Subsequent myotomy extension across the LES complex resulted in an increase in DI, as did the initial gastric myotomy extension (to 2cm distal to the EGJ). The final gastric myotomy extension (to 3cm distal) had no further effect. Conclusions During POEM, creation of the submucosal tunnel prior to myotomy resulted in a marked improvement in EGJ physiology. Myotomy extension across the LES complex and to 2cm onto the gastric wall resulted in normalization of EGJ distensibility, whereas subsequent extension to 3cm distal to the EGJ did not increase compliance further. PMID:26092005

Distensibility and pressure-flow relationship of the pulmonary circulation. II. Multibranched model.

PubMed

Bshouty, Z; Younes, M

1990-04-01

The contribution of distensibility and recruitment to the distinctive behavior of the pulmonary circulation is not known. To examine this question we developed a multibranched model in which an arterial vascular bed bifurcates sequentially up to 8 parallel channels that converge and reunite at the venous side to end in the left atrium. Eight resistors representing the capillary bed separate the arterial and venous beds. The elastic behavior of capillaries and extra-alveolar vessels was modeled after Fung and Sobin (Circ. Res. 30: 451-490, 1972) and Smith and Mitzner (J. Appl. Physiol. 48: 450-467, 1980), respectively. Forces acting on each component are modified and calculated individually, thus enabling the user to explore the effects of parallel and longitudinal heterogeneities in applied forces (e.g., gravity, vasomotor tone). Model predictions indicate that the contribution of distensibility to nonlinearities in the pressure-flow (P-F) and atrial-pulmonary arterial pressure (Pla-Ppa) relationships is substantial, whereas gravity-related recruitment contributes very little to these relationships. In addition, Pla-Ppa relationships, obtained at a constant flow, have no discriminating ability in identifying the presence or absence of a waterfall along the circulation. The P-F relationship is routinely shifted in a parallel fashion, within the physiological flow range, whenever extra forces (e.g., lung volume, tone) are applied uniformly at one or more branching levels, regardless of whether a waterfall is created. For a given applied force, the magnitude of parallel shift varies with proportion of the circulation subjected to the added force and with Pla.

A Safe and Efficient Technique for the Production of HCl/DCl Gas

ERIC Educational Resources Information Center

Mayer, Steven G.; Bard, Raymond R.; Cantrell, Kevin

2008-01-01

We present a safe and efficient technique to generate HCl/DCl gas for use in the classic physical chemistry experiment that introduces students to ro-vibrational spectroscopy. The reaction involves thionyl chloride and a mixture of water and deuterium oxide to produce HCl/DCl gas with SO[subscript 2] gas as a byproduct. The entire reaction is…

Elevated plasma B-type natriuretic peptide concentration and resistive index, but not decreased aortic distensibility, associate with impaired blood flow at popliteal artery in type 2 diabetic patients.

PubMed

Tajima, Yoshitaka; Suzuki, Eiji; Saito, Jun; Murase, Hiroshi; Horikawa, Yukio; Takeda, Jun

2015-01-01

Blood flow in lower extremity arteries is frequently impaired in diabetic patients even though they have a normal ankle-brachial index (ABI 1.0-1.4). Risk factors contributing to this lower extremity arterial disease have not been fully elucidated. We enrolled 52 type 2 diabetic patients with normal ABI and 30 age-matched nondiabetic subjects consecutively admitted to our hospital. Plasma B-type natriuretic peptide (BNP) concentrations were measured. Distensibility in ascending thoracic and abdominal aortas as well as total flow volume and resistive index at popliteal artery were evaluated by gated magnetic resonance imaging. An automatic device was used to measure ABI and brachial-ankle pulse-wave velocity (baPWV). Diabetic patients showed lower distensibility in ascending thoracic aorta (p<0.001) and total flow volume (p<0.001) and higher baPWV (p<0.001) and resistive index (p=0.005) and similar BNP and distensibility in abdominal aorta compared to nondiabetic subjects. Simple linear regression analyses revealed that distensibility in ascending thoracic (p=0.019) and abdominal (p=0.030) aortas positively as well as baPWV (p=0.020), resistive index (p<0.001) and BNP (p<0.001) negatively correlated with total flow volume. Stepwise multiple regression analysis demonstrated that increased BNP and resistive index were independent risk factors for total flow volume in diabetic patients (r(2)=0.639, p<0.001). These results indicate that increased plasma BNP levels and peripheral vascular resistance, but not decreased aortic distensibility, associate with impaired blood flow in lower extremity arteries in diabetic patients.

Inhibitory Effects and Sympathetic Mechanisms of Distension in the Distal Organs on Small Bowel Motility and Slow Waves in Canine.

PubMed

Song, Jun; Yin, Jieyun; Chen, Jiande D Z

2015-12-01

Rectal distension (RD) is known to induce intestinal dysmotility. Few studies were performed to compare effects of RD, colon distension (CD) and duodenal distension (DD) on small bowel motility. This study aimed to investigate effects and underlying mechanisms of distensions in these regions on intestinal motility and slow waves. Eight dogs chronically implanted with a duodenal fistula, a proximal colon fistula, and intestinal serosal electrodes were studied in six sessions: control, RD, CD, DD, RD + guanethidine, and CD + guanethidine. Postprandial intestinal contractions and slow waves were recorded for the assessment of intestinal motility. The electrocardiogram was recorded for the assessment of autonomic functions. (1) Isobaric RD and CD suppressed intestinal contractions (contractile index: 6.0 ± 0.4 with RD vs. 9.9 ± 0.9 at baseline, P = 0.001, 5.3 ± 0.2 with CD vs. 7.7 ± 0.8 at baseline, P = 0.008). Guanethidine at 3 mg/kg iv was able to partially block the effects. (2) RD and CD reduced the percentage of normal intestinal slow waves from 92.1 ± 2.8 to 64.2 ± 3.4 % (P < 0.001) and from 90 ± 2.7 to 69.2 ± 3.7 % (P = 0.01), respectively. Guanethidine could eliminate these inhibitory effects. (3) DD did not induce any changes in small intestinal contractions and slow waves (P > 0.05). (4) The spectral analysis of the heart rate variability showed that both RD and CD increased sympathetic activity (LF) and reduced vagal activity (HF) (P < 0.05). Isobaric RD and CD could inhibit postprandial intestinal motility and impair intestinal slow waves, which were mediated via the sympathetic pathway. However, DD at a site proximal to the measurement site did not seem to impair small intestinal contractions or slow waves.

DEVELOPMENT OF THE CHARCOAL ADSORPTION TECHNIQUE FOR DETERMINATION OF RADON CONTENT IN NATURAL GAS.

PubMed

Paewpanchon, P; Chanyotha, S

2017-11-01

A technique for the determination of the radon concentration in natural gas using charcoal adsorption has been developed to study the effects of parameters that influence the adsorption efficiency of radon onto activated charcoal. Several sets of experiments were conducted both in the laboratory and in an actual natural gas field for comparison. The results show that the adsorption capability of radon onto activated charcoal varies inversely with temperature, hydrocarbon concentration and the humidity contained within the natural gas. A technique utilizing dry ice as a coolant was found to be the most effective for trapping radon in natural gas samples at the production site. A desiccant can be used to remove moisture from the sampling gas. The technique described here increases the adsorption efficiency of activated charcoal by 10-20% compared to our previous study. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Measurement of water absorption capacity in wheat flour by a headspace gas chromatographic technique.

PubMed

Xie, Wei-Qi; Yu, Kong-Xian; Gong, Yi-Xian

2018-04-17

The purpose of this work is to introduce a new method for quantitatively analyzing water absorption capacity in wheat flour by a headspace gas chromatographic technique. This headspace gas chromatographic technique was based on measuring the water vapor released from a series of wheat flour samples with different contents of water addition. According to the different trends between the vapor and wheat flour phase before and after the water absorption capacity in wheat flour, a turning point (corresponding to water absorption capacity in wheat flour) can be obtained by fitting the data of the water gas chromatography peak area from different wheat flour samples. The data showed that the phase equilibrium in the vial can be achieved in 25 min at desired temperature (35°C). The relative standard deviation of the reaction headspace gas chromatographic technique in water absorption capacity determination was within 3.48%, the relative differences has been determined by comparing the water absorption capacity obtained from this new analytical technique with the data from the reference technique (i.e., the filtration method), which are less than 8.92%. The new headspace gas chromatographic method is automated, accurate and be a reliable tool for quantifying water absorption capacity in wheat flour in both laboratory research and mill applications. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of cholera toxin on the potential difference and motor responses induced by distension in the rat proximal small intestine in vivo.

PubMed

Kordasti, Shirin; Sapnara, Maria; Thomas, Evan A; Lindstrom, Erik; Forsman, Mikael; Bornstein, Joel C; Sjövall, Henrik

2006-05-01

Cholera toxin (CT) may induce uncontrolled firing in recurrent networks of secretomotor neurons in the submucous plexus. This hypothesis was tested in chloralose-anesthetized rats in vivo. The secretory reflex response to graded intestinal distension was measured with or without prior exposure to luminal CT. The transmural potential difference (PD) was used as a marker for electrogenic chloride secretion. In controls, distension increased PD, and this response was reduced by the neural blocker tetrodotoxin given serosally and the vasoactive intestinal peptide (VIP) receptor antagonist [4Cl-d-Phe(6),Leu(17)]VIP (2 mug.min(-1).kg(-1) iv) but unaffected by the serotonin 5-HT(3) receptor antagonist granisetron, by the nicotinic receptor antagonist hexamethonium, by the muscarinic receptor antagonist atropine, or by the cyclooxygenase inhibitor indomethacin. Basal PD increased significantly with time in CT-exposed segments, an effect blocked by granisetron, by indomethacin, and by [4Cl-d-Phe(6),Leu(17)]VIP but not by hexamethonium or atropine. In contrast, once the increased basal PD produced by CT was established, [4Cl-d-Phe(6),Leu(17)]VIP and indomethacin had no significant effect, whereas granisetron and hexamethonium markedly depressed basal PD. CT significantly reduced the increase in PD produced by distension, an effect reversed by granisetron, indomethacin, and atropine. CT also activated a specific motility response to distension, repeated cluster contractions, but only in animals pretreated with granisetron, indomethacin, or atropine. These data are compatible with the hypothesis that CT induces uncontrolled activity in submucous secretory networks. Development of this state depends on 5-HT(3) receptors, VIP receptors, and prostaglandin synthesis, whereas its maintenance depends on 5-HT(3) and nicotinic receptors but not VIP receptors. The motility effects of CT (probably reflecting myenteric activity) are partially suppressed via a mechanism involving 5-HT(3

Contribution of multiple inert gas elimination technique to pulmonary medicine. 1. Principles and information content of the multiple inert gas elimination technique.

PubMed Central

Roca, J.; Wagner, P. D.

1994-01-01

This introductory review summarises four different aspects of the multiple inert gas elimination technique (MIGET). Firstly, the historical background that facilitated, in the mid 1970s, the development of the MIGET as a tool to obtain more information about the entire spectrum of VA/Q distribution in the lung by measuring the exchange of six gases of different solubility in trace concentrations. Its principle is based on the observation that the retention (or excretion) of any gas is dependent on the solubility (lambda) of that gas and the VA/Q distribution. A second major aspect is the analysis of the information content and limitations of the technique. During the last 15 years a substantial amount of clinical research using the MIGET has been generated by several groups around the world. The technique has been shown to be adequate in understanding the mechanisms of hypoxaemia in different forms of pulmonary disease and the effects of therapeutic interventions, but also in separately determining the quantitative role of each extrapulmonary factor on systemic arterial PO2 when they change between two conditions of MIGET measurement. This information will be extensively reviewed in the forthcoming articles of this series. Next, the different modalities of the MIGET, practical considerations involved in the measurements and the guidelines for quality control have been indicated. Finally, a section has been devoted to the analysis of available data in healthy subjects under different conditions. The lack of systematic information on the VA/Q distributions of older healthy subjects is emphasised, since it will be required to fully understand the changes brought about by diseases that affect the older population. PMID:8091330

An extended proximal esophageal myotomy is necessary to normalize EGJ distensibility during Heller myotomy for achalasia, but not POEM

PubMed Central

Teitelbaum, Ezra N.; Soper, Nathaniel J.; Pandolfino, John E.; Kahrilas, Peter J.; Boris, Lubomyr; Nicodème, Frédéric; Lin, Zhiyue; Hungness, Eric S.

2015-01-01

Background For laparoscopic Heller myotomy (LHM), the optimal myotomy length proximal to the esophagogastric junction (EGJ) is unknown. In this study, we used a functional lumen imaging probe (FLIP) to measure EGJ distensibility changes resulting from variable proximal myotomy lengths during LHM and peroral esophageal myotomy (POEM). Methods Distensibility index (DI) (defined as the minimum cross-sectional area at the EGJ divided by pressure) was measured with FLIP after each operative step. During LHM and POEM, each patient’s myotomy was performed in two stages: first, a myotomy ablating only the EGJ complex was created (EGJ-M), extending from 2cm proximal to the EGJ, to 3cm distal to it. Next, the myotomy was lengthened 4cm further cephalad to create an extended proximal myotomy (EP-M). Results Measurements were performed in 12 patients undergoing LHM and 19 undergoing POEM. LHM resulted in an overall increase in DI (1.6 ±1 vs. 6.3 ±3.4 mm2/mmHg, p<.001). Creation of an EGJ-M resulted in a small increase (1.6 to 2.3 mm2/mmHg, p<.01) and extension to an EP-M resulted in a larger increase (2.3 to 4.9 mm2/mmHg, p<.001). This effect was consistent, with 11 (92%) patients experiencing a larger increase after EP-M than after EGJ-M. Fundoplication resulted in a decrease in DI and deinsufflation an increase. POEM resulted in an increase in DI (1.3 ±1 vs. 9.2 ±3.9 mm2/mmHg, p<.001). Both creation of the submucosal tunnel and performing an EGJ-M increased DI, whereas lengthening of the myotomy to an EP-M had no additional effect. POEM resulted in a larger overall increase from baseline than LHM (7.9 ±3.5 vs. 4.7 ±3.3 mm2/mmHg, p<.05). Conclusions During LHM, an extended proximal myotomy was necessary to normalize distensibility, whereas during POEM, a myotomy confined to the EGJ complex was sufficient. In this cohort, POEM resulted in a larger overall increase in EGJ distensibility. PMID:24853854

An extended proximal esophageal myotomy is necessary to normalize EGJ distensibility during Heller myotomy for achalasia, but not POEM.

PubMed

Teitelbaum, Ezra N; Soper, Nathaniel J; Pandolfino, John E; Kahrilas, Peter J; Boris, Lubomyr; Nicodème, Frédéric; Lin, Zhiyue; Hungness, Eric S

2014-10-01

For laparoscopic Heller myotomy (LHM), the optimal myotomy length proximal to the esophagogastric junction (EGJ) is unknown. In this study, we used a functional lumen imaging probe (FLIP) to measure EGJ distensibility changes resulting from variable proximal myotomy lengths during LHM and peroral esophageal myotomy (POEM). Distensibility index (DI) (defined as the minimum cross-sectional area at the EGJ divided by pressure) was measured with FLIP after each operative step. During LHM and POEM, each patient's myotomy was performed in two stages: first, a myotomy ablating only the EGJ complex was created (EGJ-M), extending from 2 cm proximal to the EGJ, to 3 cm distal to it. Next, the myotomy was lengthened 4 cm further cephalad to create an extended proximal myotomy (EP-M). Measurements were performed in 12 patients undergoing LHM and 19 undergoing POEM. LHM resulted in an overall increase in DI (1.6 ± 1 vs. 6.3 ± 3.4 mm(2)/mmHg, p < 0.001). Creation of an EGJ-M resulted in a small increase (1.6-2.3 mm(2)/mmHg, p < 0.01) and extension to an EP-M resulted in a larger increase (2.3-4.9 mm(2)/mmHg, p < 0.001). This effect was consistent, with 11 (92%) patients experiencing a larger increase after EP-M than after EGJ-M. Fundoplication resulted in a decrease in DI and deinsufflation an increase. POEM resulted in an increase in DI (1.3 ± 1 vs. 9.2 ± 3.9 mm(2)/mmHg, p < 0.001). Both creation of the submucosal tunnel and performing an EGJ-M increased DI, whereas lengthening of the myotomy to an EP-M had no additional effect. POEM resulted in a larger overall increase from baseline than LHM (7.9 ± 3.5 vs. 4.7 ± 3.3 mm(2)/mmHg, p < 0.05). During LHM, an EP-M was necessary to normalize distensibility, whereas during POEM, a myotomy confined to the EGJ complex was sufficient. In this cohort, POEM resulted in a larger overall increase in EGJ distensibility.

Multiple inert gas elimination technique by micropore membrane inlet mass spectrometry--a comparison with reference gas chromatography.

PubMed

Kretzschmar, Moritz; Schilling, Thomas; Vogt, Andreas; Rothen, Hans Ulrich; Borges, João Batista; Hachenberg, Thomas; Larsson, Anders; Baumgardner, James E; Hedenstierna, Göran

2013-10-15

The mismatching of alveolar ventilation and perfusion (VA/Q) is the major determinant of impaired gas exchange. The gold standard for measuring VA/Q distributions is based on measurements of the elimination and retention of infused inert gases. Conventional multiple inert gas elimination technique (MIGET) uses gas chromatography (GC) to measure the inert gas partial pressures, which requires tonometry of blood samples with a gas that can then be injected into the chromatograph. The method is laborious and requires meticulous care. A new technique based on micropore membrane inlet mass spectrometry (MMIMS) facilitates the handling of blood and gas samples and provides nearly real-time analysis. In this study we compared MIGET by GC and MMIMS in 10 piglets: 1) 3 with healthy lungs; 2) 4 with oleic acid injury; and 3) 3 with isolated left lower lobe ventilation. The different protocols ensured a large range of normal and abnormal VA/Q distributions. Eight inert gases (SF6, krypton, ethane, cyclopropane, desflurane, enflurane, diethyl ether, and acetone) were infused; six of these gases were measured with MMIMS, and six were measured with GC. We found close agreement of retention and excretion of the gases and the constructed VA/Q distributions between GC and MMIMS, and predicted PaO2 from both methods compared well with measured PaO2. VA/Q by GC produced more widely dispersed modes than MMIMS, explained in part by differences in the algorithms used to calculate VA/Q distributions. In conclusion, MMIMS enables faster measurement of VA/Q, is less demanding than GC, and produces comparable results.

Intelligent and integrated techniques for coalbed methane (CBM) recovery and reduction of greenhouse gas emission.

PubMed

Qianting, Hu; Yunpei, Liang; Han, Wang; Quanle, Zou; Haitao, Sun

2017-07-01

Coalbed methane (CBM) recovery is a crucial approach to realize the exploitation of a clean energy and the reduction of the greenhouse gas emission. In the past 10 years, remarkable achievements on CBM recovery have been obtained in China. However, some key difficulties still exist such as long borehole drilling in complicated geological condition, and poor gas drainage effect due to low permeability. In this study, intelligent and integrated techniques for CBM recovery are introduced. These integrated techniques mainly include underground CBM recovery techniques and ground well CBM recovery techniques. The underground CBM recovery techniques consist of the borehole formation technique, gas concentration improvement technique, and permeability enhancement technique. According to the division of mining-induced disturbance area, the ground well arrangement area and well structure type in mining-induced disturbance developing area and mining-induced disturbance stable area are optimized to significantly improve the ground well CBM recovery. Besides, automatic devices such as drilling pipe installation device are also developed to achieve remote control of data recording, which makes the integrated techniques intelligent. These techniques can provide key solutions to some long-term difficulties in CBM recovery.

GAS CHROMATOGRAPHIC TECHNIQUES FOR THE MEASUREMENT OF ISOPRENE IN AIR

EPA Science Inventory

The chapter discusses gas chromatographic techniques for measuring isoprene in air. Such measurement basically consists of three parts: (1) collection of sufficient sample volume for representative and accurate quantitation, (2) separation (if necessary) of isoprene from interfer...

Laboratory Testing of Volcanic Gas Sampling Techniques

NASA Astrophysics Data System (ADS)

Kress, V. C.; Green, R.; Ortiz, M.; Delmelle, P.; Fischer, T.

2003-12-01

results suggest that they are poor recorders of gas composition. Filter pack methods are somewhat better, but are more difficult to interpret than previously recognized. We suggest several refinements to the filter-pack technique that can improve accuracy. Giggenbach bottles remain the best method for volcanic gas sampling, despite the inherent difficulty and danger of obtaining samples in active volcanic environments. Relative merits of different alkali solutions and indicators are discussed.

Morphological comparison of PVA scaffolds obtained by gas foaming and microfluidic foaming techniques.

PubMed

Colosi, Cristina; Costantini, Marco; Barbetta, Andrea; Pecci, Raffaella; Bedini, Rossella; Dentini, Mariella

2013-01-08

In this article, we have exploited a microfluidic foaming technique for the generation of highly monodisperse gas-in-liquid bubbles as a templating system for scaffolds characterized by an ordered and homogeneous porous texture. An aqueous poly(vinyl alcohol) (PVA) solution (containing a surfactant) and a gas (argon) are injected simultaneously at constant flow rates in a flow-focusing device (FFD), in which the gas thread breaks up to form monodisperse bubbles. Immediately after its formation, the foam is collected and frozen in liquid nitrogen, freeze-dried, and cross-linked with glutaraldehyde. In order to highlight the superior morphological quality of the obtained porous material, a comparison between this scaffold and another one, also constituted of PVA but obtained with a traditional gas foaming technique, was carried out. Such a comparison has been conducted by analyzing electron microscopy and X-ray microtomographic images of the two samples. It turned out that the microfluidic produced scaffold was characterized by much more uniform porous texture than the gas-foaming one as witnessed by narrower pore size, interconnection, and wall thickness distributions. On the other side, scarce pore interconnectivity, relatively low pore volume, and limited production rate represent, by now, the principal disadvantages of microfluidic foaming as scaffold fabrication method, emphasizing the kind of improvement that this technique needs to undergo.

Dynamic technique for measuring adsorption in a gas chromatograph

NASA Technical Reports Server (NTRS)

Deuel, C. L.; Hultgren, N. W.; Mobert, M. L.

1973-01-01

Gas-chromatographic procedure, together with mathematical analysis of adsorption isotherm, allows relative surface areas and adsorptive powers for trace concentrations to be determined in a few minutes. Technique may be used to evaluate relative surface areas of different adsorbates, expressed as volume of adsorbent/gram of adsorbate, and to evaluate their relative adsorptive power.

Stress-strain analysis of contractility in the ileum in response to flow and ramp distension in streptozotocin-induced diabetic rats--association with advanced glycation end product formation.

PubMed

Zhao, Jingbo; Chen, Pengmin; Gregersen, Hans

2015-04-13

This study compared the ileal contractility and analyzed the association between contractility with advanced glycation end product (AGE) formation in normal and streptozotocin (STZ)-induced diabetic rats. Nine STZ-induced diabetic rats (Diabetes group) and 9 normal rats (Normal group) were used. The motility experiments were carried out on ileums in organ baths containing physiological Krebs solution. Ileal pressure and diameter changes were obtained from basic, flow-induced and ramp distension-induced contractions. The frequency and amplitude of contractions were analyzed from pressure-diameter curves. Distension-induced contraction thresholds and maximum contraction amplitude of basic and flow-induced contractions were calculated in terms of stress and strain. AGE and its receptor (RAGE) in the layers were detected by immunohistochemistry staining. The maximum stress of flow-induced contractions was lowest in the Diabetes Group (P<0.05). During ramp distension, the pressure and stress thresholds and Young's modulus to induce phasic contraction were lowest in the Diabetes Group (P<0.05 and P<0.01). AGE and RAGE expressions in the different ileum layers were highest in the Diabetes group. The contraction pressure and stress thresholds were significantly associated with AGE expression in the muscle layer and RAGE expression in mucosa epithelium and neurons. The diabetic intestine was hypersensitive to distension for contraction induction. However, the contraction force produced by smooth muscle was lowest in diabetic rats. Increased AGE/RAGE expression was associated with the contractility changes in diabetic rats. Copyright © 2015 Elsevier Ltd. All rights reserved.

Extended electrode technique. [gas metal arc welding of metal plates

NASA Technical Reports Server (NTRS)

Schaper, V. D.; Pollack, A.

1972-01-01

The extended electrode technique is a unique welding process which utilizes manual gas-metal-arc (GMAW) semi-automatic equipment and close, square butt joints to effectively produce a weld. The technique takes advantage of the resistance heating of the electode extension to effect the root pass. Weldments as large as 72-X30-X2-inch have been fabricated with this technique under normal shipyard welding conditions. Mechanical properties and explosion bulge tests indicate that satisfactory results are obtained with this process. Potential savings of approximately 50 percent can be achieved in flat welding and repair of heavy structural steel members.

Mississippi exploration field trials using microbial, radiometrics, free soil gas, and other techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moody, J.S.; Brown, L.R.; Thieling, S.C.

1995-12-31

The Mississippi Office of Geology has conducted field trials using the surface exploration techniques of geomicrobial, radiometrics, and free soil gas. The objective of these trials is to determine if Mississippi oil and gas fields have surface hydrocarbon expression resulting from vertical microseepage migration. Six fields have been surveyed ranging in depth from 3,330 ft to 18,500 ft. The fields differ in trapping styles and hydrocarbon type. The results so far indicate that these fields do have a surface expression and that geomicrobial analysis as well as radiometrics and free soil gas can detect hydrocarbon microseepage from pressurized reservoirs. Allmore » three exploration techniques located the reservoirs independent of depth, hydrocarbon type, or trapping style.« less

Reply to the commentary by Hillman et al. on: "Vascular distensibilities have minor effects on intracardiac shunt patterns in reptiles" by Filogonio et al. (2017).

PubMed

Filogonio, Renato; Costa Leite, Cléo Alcantara; Wang, Tobias

2017-06-01

Our meta-analysis (Filogonio et al., 2017) on central vascular blood flows in a snake (Crotalus durissus) and a turtle (Trachemys scripta) was motivated by Hillman et al.'s (2014) analysis on amphibians to investigate whether cardiac shunt patterns depend on cardiac output and vascular distensibilities. In contrast to Hillman et al. (2014), we did not uncover a general trend that supports the notion that cardiac shunts in reptiles are dictated by vascular distensibilities. In addition to our response to the criticism raised by Hillman et al. (2017), we suggest that future experiments should consider (i) both compliance and distensibility of the major arteries; (ii) differences in volume of the systemic and pulmonary circuits to account for the accommodation of stroke volume; and (iii) an evaluation of the pulsatile pressures in both the ventricle and the major arteries to consider the timing of the ventricular ejection provided by opening of the ventricular valves. We hope these suggestions may help future clarification of the relative importance of passive arterial mechanical properties compared to autonomic regulation in determining intracardiac shunts in both amphibians and reptiles. Copyright © 2017 Elsevier GmbH. All rights reserved.

Towards the development of rapid screening techniques for shale gas core properties

NASA Astrophysics Data System (ADS)

Cave, Mark R.; Vane, Christopher; Kemp, Simon; Harrington, Jon; Cuss, Robert

2013-04-01

Shale gas has been produced for many years in the U.S.A. and forms around 8% of total their natural gas production. Recent testing for gas on the Fylde Coast in Lancashire UK suggests there are potentially large reserves which could be exploited. The increasing significance of shale gas has lead to the need for deeper understanding of shale behaviour. There are many factors which govern whether a particular shale will become a shale gas resource and these include: i) Organic matter abundance, type and thermal maturity; ii) Porosity-permeability relationships and pore size distribution; iii) Brittleness and its relationship to mineralogy and rock fabric. Measurements of these properties require sophisticated and time consuming laboratory techniques (Josh et al 2012), whereas rapid screening techniques could provide timely results which could improve the efficiency and cost effectiveness of exploration. In this study, techniques which are portable and provide rapid on-site measurements (X-ray Fluorescence (XRF) and Infra-red (IR) spectroscopy) have been calibrated against standard laboratory techniques (Rock-Eval 6 analyser-Vinci Technologies) and Powder whole-rock XRD analysis was carried out using a PANalytical X'Pert Pro series diffractometer equipped with a cobalt-target tube, X'Celerator detector and operated at 45kV and 40mA, to predict properties of potential shale gas material from core material from the Bowland shale Roosecote, south Cumbria. Preliminary work showed that, amongst various mineralogical and organic matter properties of the core, regression models could be used so that the total organic carbon content could be predicted from the IR spectra with a 95 percentile confidence prediction error of 0.6% organic carbon, the free hydrocarbons could be predicted with a 95 percentile confidence prediction error of 0.6 mgHC/g rock, the bound hydrocarbons could be predicted with a 95 percentile confidence prediction error of 2.4 mgHC/g rock, mica content

Advanced liner-cooling techniques for gas turbine combustors

NASA Technical Reports Server (NTRS)

Norgren, C. T.; Riddlebaugh, S. M.

1985-01-01

Component research for advanced small gas turbine engines is currently underway at the NASA Lewis Research Center. As part of this program, a basic reverse-flow combustor geometry was being maintained while different advanced liner wall cooling techniques were investigated. Performance and liner cooling effectiveness of the experimental combustor configuration featuring counter-flow film-cooled panels is presented and compared with two previously reported combustors featuring: splash film-cooled liner walls; and transpiration cooled liner walls (Lamilloy).

Techniques for measuring ultrahigh-pressure Hugoniot equation of state on a three-stage gas gun

NASA Astrophysics Data System (ADS)

Wang, Xiang; Hu, Jianbo; Dai, Chengda; Wang, Qiangsong; Bo, Jingsong; Tan, Hua; Yu, Yuying

2011-06-01

A three-stage gas gun was developed by mounting an extending launcher tube on a two-stage gas gun, and was successfully applied to perform ultrahigh-pressure Hugoniot measurements for Ta and Pt by using this three-stage gun. Here we introduced the three-stag gas gun launcher and Hugoniot measurement techniques, including shock front shape diagnosis, shock wave velocity and impact velocity measurement as well as numerical simulation. By using this three-stage gun, Ta or Pt impactors were launched up to ~10 km/s, and the Hugoniot data were respectively measured with high accuracy up to 750 GPa for Ta and 1TPa for Pt. It is demonstrated that the three-stage gas gun is a promising technique for studying the ultrahigh-pressure properties of materials, which never before obtained by utilizing two-stage light-gas-gun.

Development of an in situ calibration technique for combustible gas detectors

NASA Technical Reports Server (NTRS)

Shumar, J. W.; Wynveen, R. A.; Lance, N., Jr.; Lantz, J. B.

1977-01-01

This paper describes the development of an in situ calibration procedure for combustible gas detectors (CGD). The CGD will be a necessary device for future space vehicles as many subsystems in the Environmental Control/Life Support System utilize or produce hydrogen (H2) gas. Existing calibration techniques are time-consuming and require support equipment such as an environmental chamber and calibration gas supply. The in situ calibration procedure involves utilization of a water vapor electrolysis cell for the automatic in situ generation of a H2/air calibration mixture within the flame arrestor of the CGD. The development effort concluded with the successful demonstration of in situ span calibrations of a CGD.

Optimal sensor locations for the backward Lagrangian stochastic technique in measuring lagoon gas emission

USDA-ARS?s Scientific Manuscript database

This study evaluated the impact of gas concentration and wind sensor locations on the accuracy of the backward Lagrangian stochastic inverse-dispersion technique (bLS) for measuring gas emission rates from a typical lagoon environment. Path-integrated concentrations (PICs) and 3-dimensional (3D) wi...

Numerical simulation of unsteady generalized Newtonian blood flow through differently shaped distensible arterial stenoses.

PubMed

Sarifuddin; Chakravarty, S; Mandal, P K; Layek, G C

2008-01-01

An updated numerical simulation of unsteady generalized Newtonian blood flow through differently shaped distensible arterial stenoses is developed. A shear-thinning fluid modelling the deformation dependent viscosity of blood is considered for the characterization of generalized Newtonian behaviour of blood. The arterial model is treated as two-dimensional and axisymmetric with an outline of the stenosis obtained from a three-dimensional casting of a mildly stenosed artery. The full Navier-Stokes equations governing blood flow are written in the dimensionless form and the solution is accomplished by finite time-step advancement through their finite difference staggered grid representations. The marker and cell (MAC) method comprising the use of a set of marker particles moving with the fluid is used for the purpose. Results are obtained for three differently shaped stenoses - irregular, smooth and cosine curve representations. The present results do agree well with those of existing investigations in the steady state, but contrary to their conclusions the present findings demonstrate that the excess pressure drop across the cosine and the smooth stenoses is caused by neither their smoothness nor their higher degree of symmetry relative to the irregular stenosis, but is rather an effect of area cover with respect to the irregular stenosis. This effect clearly prevails throughout the entire physiological range of Reynolds numbers. Further the in-depth study in flow patterns reveals the development of flow separation zones in the diverging part of the stenosis towards the arterial wall, and they are influenced by non-Newtonian blood rheology, distensibility of the wall and flow unsteadiness in order to validate the applicability of the present model.

Stress and strain analysis of contractions during ramp distension in partially obstructed guinea pig jejunal segments

PubMed Central

Zhao, Jingbo; Liao, Donghua; Yang, Jian; Gregersen, Hans

2011-01-01

Previous studies have demonstrated morphological and biomechanical remodeling in the intestine proximal to an obstruction. The present study aimed to obtain stress and strain thresholds to initiate contraction and the maximal contraction stress and strain in partially obstructed guinea pig jejunal segments. Partial obstruction and sham operations were surgically created in mid-jejunum of male guinea pigs. The animals survived 2, 4, 7, and 14 days, respectively. Animals not being operated on served as normal controls. The segments were used for no-load state, zero-stress state and distension analyses. The segment was inflated to 10 cmH2O pressure in an organ bath containing 37°C Krebs solution and the outer diameter change was monitored. The stress and strain at the contraction threshold and at maximum contraction were computed from the diameter, pressure and the zero-stress state data. Young’s modulus was determined at the contraction threshold. The muscle layer thickness in obstructed intestinal segments increased up to 300%. Compared with sham-obstructed and normal groups, the contraction stress threshold, the maximum contraction stress and the Young’s modulus at the contraction threshold increased whereas the strain threshold and maximum contraction strain decreased after 7 days obstruction (P<0.05 and 0.01). In conclusion, in the partially obstructed intestinal segments, a larger distension force was needed to evoke contraction likely due to tissue remodeling. Higher contraction stresses were produced and the contraction deformation (strain) became smaller. PMID:21632056

[Posterior capsule opacification, capsular bag distension syndrome, and anterior capsular phimosis: A retrospective cohort study].

PubMed

González-Martín-Moro, J; González-López, J J; Gómez-Sanz, F; Zarallo-Gallardo, J; Cobo-Soriano, R

2015-02-01

To determine the incidence and the risk factors involved in the development of the three main postoperative capsular complications: posterior capsule opacification (PCO), capsular bag distension syndrome (CBDS), and anterior capsular phimosis syndrome (ACP). A retrospective cohort study was conducted on 801 patients submitted to cataract surgery in the ophthalmology unit of Hospital del Henares (Madrid) from March 2, 2009 to February 28, 2010. Computerized clinical charts were reviewed during July 2012. PCO was studied using the Kaplan-Meier method (log rank test). A total of 167 patients developed PCO. No association could be demonstrated between PCO and age, sex, diabetes mellitus, phaco technique, IOL model, tamsulosin intake, glaucoma, and age-related macular degeneration. Three patients developed CBDS, all of them have received and Akreos Adapt AO(®) (Bausch & Lomb). Two of them were young men who had received surgery for posterior subcapsular cataracts. Three patients developed ACP, 2 of whom had received a MicroSlim(®) IOL (PhysIOL). No association was found between PCO and any of the studied variables. Male gender, young age, subcapsular cataract and large non-angulated lens such as Akreos Adapt AO(®) could be associated with CBDS. ACP could be more frequent when microincision IOLs (like MicroSlim(®)) are implanted. Copyright © 2013 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.

Effects of gas composition in headspace and bicarbonate concentrations in media on gas and methane production, degradability, and rumen fermentation using in vitro gas production techniques.

PubMed

Patra, Amlan Kumar; Yu, Zhongtang

2013-07-01

Headspace gas composition and bicarbonate concentrations in media can affect methane production and other characteristics of rumen fermentation in in vitro gas production systems, but these 2 important factors have not been evaluated systematically. In this study, these 2 factors were investigated with respect to gas and methane production, in vitro digestibility of feed substrate, and volatile fatty acid (VFA) profile using in vitro gas production techniques. Three headspace gas compositions (N2+ CO2+ H2 in the ratio of 90:5:5, CO2, and N2) with 2 substrate types (alfalfa hay only, and alfalfa hay and a concentrate mixture in a 50:50 ratio) in a 3×2 factorial design (experiment 1) and 3 headspace compositions (N2, N2 + CO2 in a 50:50 ratio, and CO2) with 3 bicarbonate concentrations (80, 100, and 120 mM) in a 3×3 factorial design (experiment 2) were evaluated. In experiment 1, total gas production (TGP) and net gas production (NGP) was the lowest for CO2, followed by N2, and then the gas mixture. Methane concentration in headspace gas after fermentation was greater for CO2 than for N2 and the gas mixture, whereas total methane production (TMP) and net methane production (NMP) were the greatest for CO2, followed by the gas mixture, and then N2. Headspace composition did not affect in vitro digestibility or the VFA profile, except molar percentages of propionate, which were greater for CO2 and N2 than for the gas mixture. Methane concentration in headspace gas, TGP, and NGP were affected by the interaction of headspace gas composition and substrate type. In experiment 2, increasing concentrations of CO2 in the headspace decreased TGP and NGP quadratically, but increased the concentrations of methane, NMP, and in vitro fiber digestibility linearly, and TMP quadratically. Fiber digestibility, TGP, and NGP increased linearly with increasing bicarbonate concentrations in the medium. Concentrations of methane and NMP were unaffected by bicarbonate concentration, but

Monte Carlo uncertainty analyses of a bLS inverse-dispersion technique for measuring gas emissions from livestock operations

USDA-ARS?s Scientific Manuscript database

The backward Lagrangian stochastic (bLS) inverse-dispersion technique has been used to measure fugitive gas emissions from livestock operations. The accuracy of the bLS technique, as indicated by the percentages of gas recovery in various tracer-release experiments, has generally been within ± 10% o...

A Novel Repair Technique for the Internal Thermal Control System Dual-Membrane Gas Trap

NASA Technical Reports Server (NTRS)

Leimkuehler, Thomas O.; Patel, Vipul; Reeves, Daniel R.; Holt, James M.

2005-01-01

A dual-membrane gas trap is currently used to remove gas bubbles from the Internal Thermal Control System (ITCS) coolant on board the International Space Station (ISS). The gas trap consists of concentric tube membrane pairs, comprised of outer hydrophilic tubes and inner hydrophobic fibers. Liquid coolant passes through the outer hydrophilic membrane, which traps the gas bubbles. The inner hydrophobic fiber allows the trapped gas bubbles to pass through and vent to the ambient atmosphere in the cabin. The gas trap was designed to last for the entire lifetime of the ISS, and therefore was not designed to be repaired. However, repair of these gas traps is now a necessity due to contamination from the on-orbit ITCS fluid and other sources on the ground as well as a limited supply of flight gas traps. This paper describes a novel repair technique that has been developed that will allow the refurbishment of contaminated gas traps and their return to flight use.

Molecular Rayleigh Scattering Techniques Developed for Measuring Gas Flow Velocity, Density, Temperature, and Turbulence

NASA Technical Reports Server (NTRS)

Mielke, Amy F.; Seasholtz, Richard G.; Elam, Kristie A.; Panda, Jayanta

2005-01-01

Nonintrusive optical point-wise measurement techniques utilizing the principles of molecular Rayleigh scattering have been developed at the NASA Glenn Research Center to obtain time-averaged information about gas velocity, density, temperature, and turbulence, or dynamic information about gas velocity and density in unseeded flows. These techniques enable measurements that are necessary for validating computational fluid dynamics (CFD) and computational aeroacoustic (CAA) codes. Dynamic measurements allow the calculation of power spectra for the various flow properties. This type of information is currently being used in jet noise studies, correlating sound pressure fluctuations with velocity and density fluctuations to determine noise sources in jets. These nonintrusive techniques are particularly useful in supersonic flows, where seeding the flow with particles is not an option, and where the environment is too harsh for hot-wire measurements.

Gaussian mixture model based identification of arterial wall movement for computation of distension waveform.

PubMed

Patil, Ravindra B; Krishnamoorthy, P; Sethuraman, Shriram

2015-01-01

This work proposes a novel Gaussian Mixture Model (GMM) based approach for accurate tracking of the arterial wall and subsequent computation of the distension waveform using Radio Frequency (RF) ultrasound signal. The approach was evaluated on ultrasound RF data acquired using a prototype ultrasound system from an artery mimicking flow phantom. The effectiveness of the proposed algorithm is demonstrated by comparing with existing wall tracking algorithms. The experimental results show that the proposed method provides 20% reduction in the error margin compared to the existing approaches in tracking the arterial wall movement. This approach coupled with ultrasound system can be used to estimate the arterial compliance parameters required for screening of cardiovascular related disorders.

A Case Report of Postmortem Radiography of Acute, Fatal Abdominal Distension After Binge Eating.

PubMed

Usui, Akihito; Kawasumi, Yusuke; Ishizuka, Yuya; Hosokai, Yoshiyuki; Ikeda, Tomoya; Saito, Haruo; Funayama, Masato

2016-12-01

This case report describes a woman who developed fatal gastric dilatation after binge eating. She called an ambulance because of stomach pain. When she arrived at the hospital, she did not look seriously ill. However, she rapidly became unconscious and collapsed immediately after she was laid on the examination table in a supine position. Postmortem chest x-ray and computed tomography showed right shift of the mediastinum and raised left diaphragm caused by massive gastric distension. Computed tomography showed no visible inferior vena cava. We think that her sudden deterioration was caused by movement of her stomach contents. Radiographic images provided some clues to the cause of her rapid collapse and death.

Characterization of bulbospongiosus muscle reflexes activated by urethral distension in male rats.

PubMed

Tanahashi, Masayuki; Karicheti, Venkateswarlu; Thor, Karl B; Marson, Lesley

2012-10-01

The urethrogenital reflex (UGR) is used as a surrogate model of the autonomic and somatic nerve and muscle activity that accompanies ejaculation. The UGR is evoked by distension of the urethra and activation of penile afferents. The current study compares two methods of elevating urethral intraluminal pressure in spinalized, anesthetized male Sprague-Dawley rats (n = 60). The first method, penile extension UGR, involves extracting the penis from the foreskin, so that urethral pressure rises due to a natural anatomical flexure in the penis. The second method, penile clamping UGR, involves penile extension UGR with the addition of clamping of the glans penis. Groups of animals were prepared that either received no additional treatment, surgical shams, or received bilateral nerve cuts (4 nerve cut groups): either the pudendal sensory nerve branch (SbPN), the pelvic nerves, the hypogastric nerves, or all three nerves. Penile clamping UGR was characterized by multiple bursts, monitored by electromyography (EMG) of the bulbospongiosus muscle (BSM) accompanied by elevations in urethral pressure. The penile clamping UGR activity declined across multiple trials and eventually resulted in only a single BSM burst, indicating desensitization. In contrast, the penile extension UGR, without penile clamping, evoked only a single BSM EMG burst that showed no desensitization. Thus, the UGR is composed of two BSM patterns: an initial single burst, termed urethrobulbospongiosus (UBS) reflex and a subsequent multiple bursting pattern (termed ejaculation-like response, ELR) that was only induced with penile clamping urethral occlusion. Transection of the SbPN eliminated the ELR in the penile clamping model, but the single UBS reflex remained in both the clamping and extension models. Pelvic nerve (PelN) transection increased the threshold for inducing BSM activation with both methods of occlusion but actually unmasked an ELR in the penile extension method. Hypogastric nerve (HgN) cuts

Use of a microwave diagnostics technique to measure the temperature of an axisymmetric ionized gas flow

NASA Astrophysics Data System (ADS)

Tsel'Sov, Iu. G.; Kondrat'ev, A. S.

1990-12-01

A method is developed for determining the temperature of an ionized gas on the basis of electron-density sounding. This technique is used to measure the cross-sectional temperature distribution of an axisymmetric ionized gas flow using microwave diagnostics.

Stress-strain analysis of jejunal contractility in response to flow and ramp distension in type 2 diabetic GK rats: effect of carbachol stimulation.

PubMed

Zhao, Jingbo; Chen, Pengmin; Gregersen, Hans

2013-09-27

Investigation of intestinal motility in a genetic model of GK rats abandons the possible neurotoxic effect of streptozotocin in streptozotocin-induced diabetic model. Seven GK male rats (GK group) and nine normal Wistar rats (Normal group) were used in the study. The motility experiments were carried out in an organ bath containing physiological Krebs solution. Before and after 10(-5)M carbachol application, the pressure and diameter changes of jejunum were obtained in relation to (1) basic contraction, (2) flow-induced contraction with different outlet resistance pressures and (3) contractions induced by ramp distension. The frequency and amplitude of contractions were analyzed from pressure-diameter curves. Distension-induced contraction thresholds and maximum contraction amplitude of basic and flow-induced contractions were calculated in terms of stress and strain. (1) The contraction amplitude increased to the peak value in less than 10s after adding carbachol. More than two peaks were observed in the GK group. (2) Carbachol decreased the pressure and stress threshold and Young's modulus in the GK group (P<0.01). (3) Carbachol increased the maximum pressure and stress of flow-induced contractions at most outlet pressure levels in both two groups (P<0.001). Furthermore, the flow-induced contractions were significantly bigger at low outlet pressure levels in GK group (P<0.05 and P<0.01). (4) The contraction frequency, the strain threshold and the maximum contraction strain did not differ between the two groups (P>0.05) and between before and after carbachol application (P>0.05). In GK diabetic rats, the jejunal contractility was hypersensitive to flow and distension stimulation after carbachol application. Copyright © 2013 Elsevier Ltd. All rights reserved.

Preliminary evaluation of several nondestructive-evaluation techniques for silicon nitride gas-turbine rotors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kupperman, D. S.; Sciammarella, C.; Lapinski, N. P.

1978-01-01

Several nondestructive-evaluation (NDE) techniques have been examined to establish their effectiveness for detecting critically sized flaws in silicon nitride gas-turbine rotors. Preliminary results have been obtained for holographic interferometry, acoustic microscopy, dye-enhanced radiography, acoustic emission, and acoustic-impact testing techniques. This report discusses the relative effectiveness of these techniques in terms of their applicability to the rotor geometry and ability to detect critically sized flaws. Where feasible, flaw indications were verified by alternative NDE techniques or destructive examination. This study has indicated that, since the various techniques have different advantages, ultimately a reliable interrogation of ceramic rotors may require the applicationmore » of several NDE methods.« less

Direct analysis of ultra-trace semiconductor gas by inductively coupled plasma mass spectrometry coupled with gas to particle conversion-gas exchange technique.

PubMed

Ohata, Masaki; Sakurai, Hiromu; Nishiguchi, Kohei; Utani, Keisuke; Günther, Detlef

2015-09-03

An inductively coupled plasma mass spectrometry (ICPMS) coupled with gas to particle conversion-gas exchange technique was applied to the direct analysis of ultra-trace semiconductor gas in ambient air. The ultra-trace semiconductor gases such as arsine (AsH3) and phosphine (PH3) were converted to particles by reaction with ozone (O3) and ammonia (NH3) gases within a gas to particle conversion device (GPD). The converted particles were directly introduced and measured by ICPMS through a gas exchange device (GED), which could penetrate the particles as well as exchange to Ar from either non-reacted gases such as an air or remaining gases of O3 and NH3. The particle size distribution of converted particles was measured by scanning mobility particle sizer (SMPS) and the results supported the elucidation of particle agglomeration between the particle converted from semiconductor gas and the particle of ammonium nitrate (NH4NO3) which was produced as major particle in GPD. Stable time-resolved signals from AsH3 and PH3 in air were obtained by GPD-GED-ICPMS with continuous gas introduction; however, the slightly larger fluctuation, which could be due to the ionization fluctuation of particles in ICP, was observed compared to that of metal carbonyl gas in Ar introduced directly into ICPMS. The linear regression lines were obtained and the limits of detection (LODs) of 1.5 pL L(-1) and 2.4 nL L(-1) for AsH3 and PH3, respectively, were estimated. Since these LODs revealed sufficiently lower values than the measurement concentrations required from semiconductor industry such as 0.5 nL L(-1) and 30 nL L(-1) for AsH3 and PH3, respectively, the GPD-GED-ICPMS could be useful for direct and high sensitive analysis of ultra-trace semiconductor gas in air. Copyright © 2015 Elsevier B.V. All rights reserved.

Accuracy of vertical radial plume mapping technique in measuring lagoon gas emission

USDA-ARS?s Scientific Manuscript database

Recently, the U.S. Environmental Protection Agency (USEPA) posted a ground-based optical remote sensing method on its website called OTM 10 for measuring fugitive gas emission flux from area sources such as closed landfills. The OTM 10 utilizes the vertical radial plume mapping (VRPM) technique to c...

Monitoring fugitive methane and natural gas emissions, validation of measurement techniques.

NASA Astrophysics Data System (ADS)

Robinson, Rod; Innocenti, Fabrizio; Gardiner, Tom; Helmore, Jon; Finlayson, Andrew; Connor, Andy

2017-04-01

The detection and quantification of fugitive and diffuse methane emissions has become an increasing priority in recent years. As the requirements for routine measurement to support industry initiatives increase there is a growing requirement to assess and validate the performance of fugitive emission measurement technologies. For reported emissions traceability and comparability of measurements is important. This talk will present recent work addressing these needs. Differential Absorption Lidar (DIAL) is a laser based remote sensing technology, able to map the concentration of gases in the atmosphere and determine emission fluxes for fugitive emissions. A description of the technique and its application for determining fugitive emissions of methane from oil and gas operations and waste management sites will be given. As DIAL has gained acceptance as a powerful tool for the measurement and quantification of fugitive emissions, and given the rich data it produces, it is being increasingly used to assess and validate other measurement approaches. In addition, to support the validation of technologies, we have developed a portable controlled release facility able to simulate the emissions from area sources. This has been used to assess and validate techniques which are used to monitor emissions. The development and capabilities of the controlled release facility will be described. This talk will report on recent studies using DIAL and the controlled release facility to validate fugitive emission measurement techniques. This includes side by side comparisons of two DIAL systems, the application of both the DIAL technique and the controlled release facility in a major study carried out in 2015 by South Coast Air Quality Management District (SCAQMD) in which a number of optical techniques were assessed and the development of a prototype method validation approach for techniques used to measure methane emissions from shale gas sites. In conclusion the talk will provide an

The development of an electrochemical technique for in situ calibrating of combustible gas detectors

NASA Technical Reports Server (NTRS)

Shumar, J. W.; Lantz, J. B.; Schubert, F. H.

1976-01-01

A program to determine the feasibility of performing in situ calibration of combustible gas detectors was successfully completed. Several possible techniques for performing the in situ calibration were proposed. The approach that showed the most promise involved the use of a miniature water vapor electrolysis cell for the generation of hydrogen within the flame arrestor of a combustible gas detector to be used for the purpose of calibrating the combustible gas detectors. A preliminary breadboard of the in situ calibration hardware was designed, fabricated and assembled. The breadboard equipment consisted of a commercially available combustible gas detector, modified to incorporate a water vapor electrolysis cell, and the instrumentation required for controlling the water vapor electrolysis and controlling and calibrating the combustible gas detector. The results showed that operation of the water vapor electrolysis at a given current density for a specific time period resulted in the attainment of a hydrogen concentration plateau within the flame arrestor of the combustible gas detector.

Synthesis of ZnO thin film by sol-gel spin coating technique for H2S gas sensing application

NASA Astrophysics Data System (ADS)

Nimbalkar, Amol R.; Patil, Maruti G.

2017-12-01

In this present work, zinc oxide (ZnO) thin film synthesized by a simple sol-gel spin coating technique. The structural, morphology, compositional, microstructural, optical, electrical and gas sensing properties of the film were studied by using XRD, FESEM, EDS, XPS, HRTEM, Raman, FTIR and UV-vis techniques. The ZnO thin film shows hexagonal wurtzite structure with a porous structured morphology. Gas sensing performance of synthesized ZnO thin film was tested initially for H2S gas at different operating temperatures as well as concentrations. The maximum gas response is achieved towards H2S gas at 300 °C operating temperature, at 100 ppm gas concentration as compared to other gases like CH3OH, Cl2, NH3, LPG, CH3COCH3, and C2H5OH with a good stability.

Large-volume constant-concentration sampling technique coupling with surface-enhanced Raman spectroscopy for rapid on-site gas analysis

NASA Astrophysics Data System (ADS)

Zhang, Zhuomin; Zhan, Yisen; Huang, Yichun; Li, Gongke

2017-08-01

In this work, a portable large-volume constant-concentration (LVCC) sampling technique coupling with surface-enhanced Raman spectroscopy (SERS) was developed for the rapid on-site gas analysis based on suitable derivatization methods. LVCC sampling technique mainly consisted of a specially designed sampling cell including the rigid sample container and flexible sampling bag, and an absorption-derivatization module with a portable pump and a gas flowmeter. LVCC sampling technique allowed large, alterable and well-controlled sampling volume, which kept the concentration of gas target in headspace phase constant during the entire sampling process and made the sampling result more representative. Moreover, absorption and derivatization of gas target during LVCC sampling process were efficiently merged in one step using bromine-thiourea and OPA-NH4+ strategy for ethylene and SO2 respectively, which made LVCC sampling technique conveniently adapted to consequent SERS analysis. Finally, a new LVCC sampling-SERS method was developed and successfully applied for rapid analysis of trace ethylene and SO2 from fruits. It was satisfied that trace ethylene and SO2 from real fruit samples could be actually and accurately quantified by this method. The minor concentration fluctuations of ethylene and SO2 during the entire LVCC sampling process were proved to be < 4.3% and 2.1% respectively. Good recoveries for ethylene and sulfur dioxide from fruit samples were achieved in range of 95.0-101% and 97.0-104% respectively. It is expected that portable LVCC sampling technique would pave the way for rapid on-site analysis of accurate concentrations of trace gas targets from real samples by SERS.

Large-volume constant-concentration sampling technique coupling with surface-enhanced Raman spectroscopy for rapid on-site gas analysis.

PubMed

Zhang, Zhuomin; Zhan, Yisen; Huang, Yichun; Li, Gongke

2017-08-05

In this work, a portable large-volume constant-concentration (LVCC) sampling technique coupling with surface-enhanced Raman spectroscopy (SERS) was developed for the rapid on-site gas analysis based on suitable derivatization methods. LVCC sampling technique mainly consisted of a specially designed sampling cell including the rigid sample container and flexible sampling bag, and an absorption-derivatization module with a portable pump and a gas flowmeter. LVCC sampling technique allowed large, alterable and well-controlled sampling volume, which kept the concentration of gas target in headspace phase constant during the entire sampling process and made the sampling result more representative. Moreover, absorption and derivatization of gas target during LVCC sampling process were efficiently merged in one step using bromine-thiourea and OPA-NH 4 + strategy for ethylene and SO 2 respectively, which made LVCC sampling technique conveniently adapted to consequent SERS analysis. Finally, a new LVCC sampling-SERS method was developed and successfully applied for rapid analysis of trace ethylene and SO 2 from fruits. It was satisfied that trace ethylene and SO 2 from real fruit samples could be actually and accurately quantified by this method. The minor concentration fluctuations of ethylene and SO 2 during the entire LVCC sampling process were proved to be <4.3% and 2.1% respectively. Good recoveries for ethylene and sulfur dioxide from fruit samples were achieved in range of 95.0-101% and 97.0-104% respectively. It is expected that portable LVCC sampling technique would pave the way for rapid on-site analysis of accurate concentrations of trace gas targets from real samples by SERS. Copyright © 2017 Elsevier B.V. All rights reserved.

Conventional and dense gas techniques for the production of liposomes: a review.

PubMed

Meure, Louise A; Foster, Neil R; Dehghani, Fariba

2008-01-01

The aim of this review paper is to compare the potential of various techniques developed for production of homogenous, stable liposomes. Traditional techniques, such as Bangham, detergent depletion, ether/ethanol injection, reverse-phase evaporation and emulsion methods, were compared with the recent advanced techniques developed for liposome formation. The major hurdles for scaling up the traditional methods are the consumption of large quantities of volatile organic solvent, the stability and homogeneity of the liposomal product, as well as the lengthy multiple steps involved. The new methods have been designed to alleviate the current issues for liposome formulation. Dense gas liposome techniques are still in their infancy, however they have remarkable advantages in reducing the use of organic solvents, providing fast, single-stage production and producing stable, uniform liposomes. Techniques such as the membrane contactor and heating methods are also promising as they eliminate the use of organic solvent, however high temperature is still required for processing.

Polycyclic aromatic hydrocarbons, brachial artery distensibility and blood pressure among children residing near an oil refinery

PubMed Central

Trasande, Leonardo; Urbina, Elaine M.; Khoder, Mamdouh; Alghamdi, Mansour; Shabaj, Ibrahim; Alam, Mohammed S.; Harrison, Roy M.; Shamy, Magdy

2017-01-01

Background Polycyclic aromatic hydrocarbons (PAH) are produced by the burning and processing of fuel oils, and have been associated with oxidant stress, insulin resistance and hypertension in adults. Few studies have examined whether adolescents are susceptible to cardiovascular effects of PAHs. Objective To study associations of PAH exposure with blood pressure (BP) and brachial artery distensibility (BAD), an early marker of arterial wall stiffness, in young boys attending three schools in Jeddah, Saudi Arabia in varying proximity to an oil refinery. Methods Air samples collected from the three schools were analyzed for PAHs. PAH metabolites (total hydroxyphenanthrenes and 1-hydroxypyrene) were measured in urine samples from 184 adolescent males, in whom anthropometrics, heart rate, pulse pressure, brachial artery distensibility and blood pressure were measured. Descriptive, bivariate and multivariable analyses were performed to assess relationships of school location and urinary PAH metabolites with cardiovascular measures. Results Total suspended matter was significantly higher (444 ± 143 µg/m3) at the school near the refinery compared to a school located near a ring road (395 ± 65 µg/m3) and a school located away from vehicle traffic (232 ± 137 µg/m3), as were PAHs. Systolic (0.47 SD units, p = 0.006) and diastolic (0.53 SD units, p < 0.001) BP Z-scores were highest at the school near the refinery, with a 4.36-fold increase in prehypertension (p = 0.001), controlling for confounders. No differences in pulse pressure, BAD and heart rate were noted in relationship to school location. Urinary total hydroxyphenanthrenes and 1-hydroxypyrene were not associated with cardiovascular outcomes. Conclusions Proximity to an oil refinery in Saudi Arabia is associated with prehypertension and increases in PAH and particulate matter exposures. Further study including insulin resistance measurements, better control for confounding, and longitudinal measurement is

Polycyclic aromatic hydrocarbons, brachial artery distensibility and blood pressure among children residing near an oil refinery.

PubMed

Trasande, Leonardo; Urbina, Elaine M; Khoder, Mamdouh; Alghamdi, Mansour; Shabaj, Ibrahim; Alam, Mohammed S; Harrison, Roy M; Shamy, Magdy

2015-01-01

Polycyclic aromatic hydrocarbons (PAH) are produced by the burning and processing of fuel oils, and have been associated with oxidant stress, insulin resistance and hypertension in adults. Few studies have examined whether adolescents are susceptible to cardiovascular effects of PAHs. To study associations of PAH exposure with blood pressure (BP) and brachial artery distensibility (BAD), an early marker of arterial wall stiffness, in young boys attending three schools in Jeddah, Saudi Arabia in varying proximity to an oil refinery. Air samples collected from the three schools were analyzed for PAHs. PAH metabolites (total hydroxyphenanthrenes and 1-hydroxypyrene) were measured in urine samples from 184 adolescent males, in whom anthropometrics, heart rate, pulse pressure, brachial artery distensibility and blood pressure were measured. Descriptive, bivariate and multivariable analyses were performed to assess relationships of school location and urinary PAH metabolites with cardiovascular measures. Total suspended matter was significantly higher (444 ± 143 μg/m(3)) at the school near the refinery compared to a school located near a ring road (395 ± 65 μg/m(3)) and a school located away from vehicle traffic (232 ± 137 μg/m(3)), as were PAHs. Systolic (0.47 S D units, p = 0.006) and diastolic (0.53 SD units, p < 0.001) BP Z-scores were highest at the school near the refinery, with a 4.36-fold increase in prehypertension (p = 0.001), controlling for confounders. No differences in pulse pressure, BAD and heart rate were noted in relationship to school location. Urinary total hydroxyphenanthrenes and 1-hydroxypyrene were not associated with cardiovascular outcomes. Proximity to an oil refinery in Saudi Arabia is associated with prehypertension and increases in PAH and particulate matter exposures. Further study including insulin resistance measurements, better control for confounding, and longitudinal measurement is indicated. Copyright © 2014 Elsevier Inc. All

Microwave interferometry technique for obtaining gas interface velocity measurements in an expansion tube facility

NASA Technical Reports Server (NTRS)

Laney, C. C., Jr.

1974-01-01

A microwave interferometer technique to determine the front interface velocity of a high enthalpy gas flow, is described. The system is designed to excite a standing wave in an expansion tube, and to measure the shift in this standing wave as it is moved by the test gas front. Data, in the form of a varying sinusoidal signal, is recorded on a high-speed drum camera-oscilloscope combination. Measurements of average and incremental velocities in excess of 6,000 meters per second were made.

Sabots, Obturator and Gas-In-Launch Tube Techniques for Heat Flux Models in Ballistic Ranges

NASA Technical Reports Server (NTRS)

Bogdanoff, David W.; Wilder, Michael C.

2013-01-01

For thermal protection system (heat shield) design for space vehicle entry into earth and other planetary atmospheres, it is essential to know the augmentation of the heat flux due to vehicle surface roughness. At the NASA Ames Hypervelocity Free Flight Aerodynamic Facility (HFFAF) ballistic range, a campaign of heat flux studies on rough models, using infrared camera techniques, has been initiated. Several phenomena can interfere with obtaining good heat flux data when using this measuring technique. These include leakage of the hot drive gas in the gun barrel through joints in the sabot (model carrier) to create spurious thermal imprints on the model forebody, deposition of sabot material on the model forebody, thereby changing the thermal properties of the model surface and unknown in-barrel heating of the model. This report presents developments in launch techniques to greatly reduce or eliminate these problems. The techniques include the use of obturator cups behind the launch package, enclosed versus open front sabot designs and the use of hydrogen gas in the launch tube. Attention also had to be paid to the problem of the obturator drafting behind the model and impacting the model. Of the techniques presented, the obturator cups and hydrogen in the launch tube were successful when properly implemented

Understanding Methane Emission from Natural Gas Activities Using Inverse Modeling Techniques

NASA Astrophysics Data System (ADS)

Abdioskouei, M.; Carmichael, G. R.

2015-12-01

Natural gas (NG) has been promoted as a bridge fuel that can smooth the transition from fossil fuels to zero carbon energy sources by having lower carbon dioxide emission and lower global warming impacts in comparison to other fossil fuels. However, the uncertainty around the estimations of methane emissions from NG systems can lead to underestimation of climate and environmental impacts of using NG as a replacement for coal. Accurate estimates of methane emissions from NG operations is crucial for evaluation of environmental impacts of NG extraction and at larger scale, adoption of NG as transitional fuel. However there is a great inconsistency within the current estimates. Forward simulation of methane from oil and gas operation sites for the US is carried out based on NEI-2011 using the WRF-Chem model. Simulated values are compared against measurements of observations from different platforms such as airborne (FRAPPÉ field campaign) and ground-based measurements (NOAA Earth System Research Laboratory). A novel inverse modeling technique is used in this work to improve the model fit to the observation values and to constrain methane emission from oil and gas extraction sites.

Analytical Modelling of the Effects of Different Gas Turbine Cooling Techniques on Engine Performance =

NASA Astrophysics Data System (ADS)

Uysal, Selcuk Can

In this research, MATLAB SimulinkRTM was used to develop a cooled engine model for industrial gas turbines and aero-engines. The model consists of uncooled on-design, mean-line turbomachinery design and a cooled off-design analysis in order to evaluate the engine performance parameters by using operating conditions, polytropic efficiencies, material information and cooling system details. The cooling analysis algorithm involves a 2nd law analysis to calculate losses from the cooling technique applied. The model is used in a sensitivity analysis that evaluates the impacts of variations in metal Biot number, thermal barrier coating Biot number, film cooling effectiveness, internal cooling effectiveness and maximum allowable blade temperature on main engine performance parameters of aero and industrial gas turbine engines. The model is subsequently used to analyze the relative performance impact of employing Anti-Vortex Film Cooling holes (AVH) by means of data obtained for these holes by Detached Eddy Simulation-CFD Techniques that are valid for engine-like turbulence intensity conditions. Cooled blade configurations with AVH and other different external cooling techniques were used in a performance comparison study. (Abstract shortened by ProQuest.).

Conductive Polymer Synthesis with Single-Crystallinity via a Novel Plasma Polymerization Technique for Gas Sensor Applications.

PubMed

Park, Choon-Sang; Kim, Dong Ha; Shin, Bhum Jae; Kim, Do Yeob; Lee, Hyung-Kun; Tae, Heung-Sik

2016-09-30

This study proposes a new nanostructured conductive polymer synthesis method that can grow the single-crystalline high-density plasma-polymerized nanoparticle structures by enhancing the sufficient nucleation and fragmentation of the pyrrole monomer using a novel atmospheric pressure plasma jet (APPJ) technique. Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FE-SEM) results show that the plasma-polymerized pyrrole (pPPy) nanoparticles have a fast deposition rate of 0.93 µm·min -1 under a room-temperature process and have single-crystalline characteristics with porous properties. In addition, the single-crystalline high-density pPPy nanoparticle structures were successfully synthesized on the glass, plastic, and interdigitated gas sensor electrode substrates using a novel plasma polymerization technique at room temperature. To check the suitability of the active layer for the fabrication of electrochemical toxic gas sensors, the resistance variations of the pPPy nanoparticles grown on the interdigitated gas sensor electrodes were examined by doping with iodine. As a result, the proposed APPJ device could obtain the high-density and ultra-fast single-crystalline pPPy thin films for various gas sensor applications. This work will contribute to the design of highly sensitive gas sensors adopting the novel plasma-polymerized conductive polymer as new active layer.

Yb-doped large-mode-area laser fiber fabricated by halide-gas-phase-doping technique

NASA Astrophysics Data System (ADS)

Peng, Kun; Wang, Yuying; Ni, Li; Wang, Zhen; Gao, Cong; Zhan, Huan; Wang, Jianjun; Jing, Feng; Lin, Aoxiang

2015-06-01

In this manuscript, we designed a rare-earth-halide gas-phase-doping setup to fabricate a large-mode-area fiber for high power laser applications. YbCl3 and AlCl3 halides are evaporated, carried respectively and finally mixed with usual host gas material SiCl4 at the hot zone of MCVD system. Owing to the all-gas-phasing reaction process and environment, the home-made Yb-doped fiber preform has a homogeneous large core and modulated refractive index profile to keep high beam quality. The drawn fiber core has a small numerical aperture of 0.07 and high Yb concentration of 9500 ppm. By using a master oscillator power amplifier system, nearly kW-level (951 W) laser output power was obtained with a slope efficiency of 83.3% at 1063.8 nm, indicating the competition and potential of the halide-gas-phase-doping technique for high power laser fiber fabrication.

Growth of single wall carbon nanotubes using PECVD technique: An efficient chemiresistor gas sensor

NASA Astrophysics Data System (ADS)

Lone, Mohd Yaseen; Kumar, Avshish; Husain, Samina; Zulfequar, M.; Harsh; Husain, Mushahid

2017-03-01

In this work, the uniform and vertically aligned single wall carbon nanotubes (SWCNTs) have been grown on Iron (Fe) deposited Silicon (Si) substrate by plasma enhanced chemical vapor deposition (PECVD) technique at very low temperature of 550 °C. The as-grown samples of SWCNTS were characterized by field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM) and Raman spectrometer. SWCNT based chemiresistor gas sensing device was fabricated by making the proper gold contacts on the as-grown SWCNTs. The electrical conductance and sensor response of grown SWCNTs have been investigated. The fabricated SWCNT sensor was exposed to ammonia (NH3) gas at 200 ppm in a self assembled apparatus. The sensor response was measured at room temperature which was discussed in terms of adsorption of NH3 gas molecules on the surface of SWCNTs. The achieved results are used to develope a miniaturized gas sensor device for monitoring and control of environment pollutants.

Development and in-vivo assessment of the bioavailability of oridonin solid dispersions by the gas anti-solvent technique.

PubMed

Li, Songming; Liu, Ying; Liu, Tao; Zhao, Ling; Zhao, Jihui; Feng, Nianping

2011-06-15

We developed solid dispersions, using the gas anti-solvent technique (GAS), to improve the oral bioavailability of the poorly water-soluble active component oridonin. The solubility of oridonin in supercritical carbon dioxide was measured under various pressures and temperatures. To prepare oridonin solid dispersions using the GAS technique, ethanol was used as the solvent, CO(2) was used as the anti-solvent and the hydrophilic polymer polyvinylpyrrolidone K17 (PVP K17) was used as the drug carrier matrix. Characterization of the obtained preparations was undertaken using scanning electron microscopy (SEM), X-ray diffraction (XRD) analyses and a drug release study. Oridonin solid dispersions were formed and oridonin was present in an amorphous form in these dispersions. Oridonin solid dispersions significantly increased the drug dissolution rate compared with that of oridonin powder, primarily through drug amorphization. Compared with the physical mixture of oridonin and PVP K17, oridonin solid dispersions gave higher values of AUC and C(max), and the absorption of oridonin from solid dispersions resulted in 26.4-fold improvement in bioavailability. The present study illustrated the feasibility of applying the GAS technique to prepare oridonin solid dispersions, and of using them for the delivery of oridonin via the oral route. Copyright © 2011 Elsevier B.V. All rights reserved.

Application of a support vector machine algorithm to the safety precaution technique of medium-low pressure gas regulators

NASA Astrophysics Data System (ADS)

Hao, Xuejun; An, Xaioran; Wu, Bo; He, Shaoping

2018-02-01

In the gas pipeline system, safe operation of a gas regulator determines the stability of the fuel gas supply, and the medium-low pressure gas regulator of the safety precaution system is not perfect at the present stage in the Beijing Gas Group; therefore, safety precaution technique optimization has important social and economic significance. In this paper, according to the running status of the medium-low pressure gas regulator in the SCADA system, a new method for gas regulator safety precaution based on the support vector machine (SVM) is presented. This method takes the gas regulator outlet pressure data as input variables of the SVM model, the fault categories and degree as output variables, which will effectively enhance the precaution accuracy as well as save significant manpower and material resources.

A double sealing technique for increasing the precision of headspace-gas chromatographic analysis.

PubMed

Xie, Wei-Qi; Yu, Kong-Xian; Gong, Yi-Xian

2018-01-19

This paper investigates a new double sealing technique for increasing the precision of the headspace gas chromatographic method. The air leakage problem caused by the high pressure in the headspace vial during the headspace sampling process has a great impact to the measurement precision in the conventional headspace analysis (i.e., single sealing technique). The results (using ethanol solution as the model sample) show that the present technique is effective to minimize such a problem. The double sealing technique has an excellent measurement precision (RSD < 0.15%) and accuracy (recovery = 99.1%-100.6%) for the ethanol quantification. The detection precision of the present method was 10-20 times higher than that in earlier HS-GC work that use conventional single sealing technique. The present double sealing technique may open up a new avenue, and also serve as a general strategy for improving the performance (i.e., accuracy and precision) of headspace analysis of various volatile compounds. Copyright © 2017 Elsevier B.V. All rights reserved.

Adaptive polynomial chaos techniques for uncertainty quantification of a gas cooled fast reactor transient

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perko, Z.; Gilli, L.; Lathouwers, D.

2013-07-01

Uncertainty quantification plays an increasingly important role in the nuclear community, especially with the rise of Best Estimate Plus Uncertainty methodologies. Sensitivity analysis, surrogate models, Monte Carlo sampling and several other techniques can be used to propagate input uncertainties. In recent years however polynomial chaos expansion has become a popular alternative providing high accuracy at affordable computational cost. This paper presents such polynomial chaos (PC) methods using adaptive sparse grids and adaptive basis set construction, together with an application to a Gas Cooled Fast Reactor transient. Comparison is made between a new sparse grid algorithm and the traditionally used techniquemore » proposed by Gerstner. An adaptive basis construction method is also introduced and is proved to be advantageous both from an accuracy and a computational point of view. As a demonstration the uncertainty quantification of a 50% loss of flow transient in the GFR2400 Gas Cooled Fast Reactor design was performed using the CATHARE code system. The results are compared to direct Monte Carlo sampling and show the superior convergence and high accuracy of the polynomial chaos expansion. Since PC techniques are easy to implement, they can offer an attractive alternative to traditional techniques for the uncertainty quantification of large scale problems. (authors)« less

Application of plasma gas modulation technique for improvement of the measurement of Mn emission intensity in ICP-AES.

PubMed

Kubota, K; Wagatsuma, K

2001-01-02

A phase-sensitive detection technique associated with a digital lock-in amplifier was applied for an improvement of the detection in ICP-AES. The lock-in amplifier works as an extremely narrow band pass filter. It can pick up the modulated signal, which has the same frequency as the reference signal, from any noise and thus it can improve the signal-to-noise ratio. Modulation of the ICP can be performed by mixing small amounts of air to argon as the outer gas cyclically, because the emission intensities of ionic lines are enhanced by using the mixed gas. An electromagnetic valve, which is placed in the outer-gas flow path, causes periodic variation in the air gas in the outer-gas flow, and thus switching the valve on/off can modulate the ICP. By choosing the appropriate conditions, the addition of air gas enhances the emission intensity of ionic lines more than that of the background, thus leading to improved signal-to-background ratios. At the same time the lock-in amplifier further enhances the ionic emissions because it picks up only the modulated part of the signal. By applying the plasma gas flow modulation technique the detection and the determination limits of the Mn II 257.610 nm line are improved in comparison with the conventional method. A change in plasma shape corresponding to the modulation frequency is observed when the ICP is modulated.

Low Cost Gas Turbine Off-Design Prediction Technique

NASA Astrophysics Data System (ADS)

Martinjako, Jeremy

This thesis seeks to further explore off-design point operation of gas turbines and to examine the capabilities of GasTurb 12 as a tool for off-design analysis. It is a continuation of previous thesis work which initially explored the capabilities of GasTurb 12. The research is conducted in order to: 1) validate GasTurb 12 and, 2) predict off-design performance of the Garrett GTCP85-98D located at the Arizona State University Tempe campus. GasTurb 12 is validated as an off-design point tool by using the program to predict performance of an LM2500+ marine gas turbine. Haglind and Elmegaard (2009) published a paper detailing a second off-design point method and it includes the manufacturer's off-design point data for the LM2500+. GasTurb 12 is used to predict off-design point performance of the LM2500+ and compared to the manufacturer's data. The GasTurb 12 predictions show good correlation. Garrett has published specification data for the GTCP85-98D. This specification data is analyzed to determine the design point and to comment on off-design trends. Arizona State University GTCP85-98D off-design experimental data is evaluated. Trends presented in the data are commented on and explained. The trends match the expected behavior demonstrated in the specification data for the same gas turbine system. It was originally intended that a model of the GTCP85-98D be constructed in GasTurb 12 and used to predict off-design performance. The prediction would be compared to collected experimental data. This is not possible because the free version of GasTurb 12 used in this research does not have a module to model a single spool turboshaft. This module needs to be purchased for this analysis.

A novel technique: Carbon dioxide gas-assisted total peritonectomy, diaphragm and intestinal meso stripping in open surgery for advanced ovarian cancer (Çukurova technique).

PubMed

Khatib, Ghanim; Guzel, Ahmet Baris; Gulec, Umran Kucukgoz; Vardar, Mehmet Ali

2017-09-01

Most of the ovarian cancers are diagnosed at advanced stages. As peritoneal carcinomatosis increases, especially when it extends to the diaphragm and intestinal mesos, probability of obtaining complete cytoreduction is reduced. Complete cytoreduction (residue zero: R0) is one of the main factors affecting survival [1-3]. Here we present a novel technique of stripping the peritoneal surfaces as a part of cytoreductive surgery in such cases. A 55year-old woman diagnosed with peritoneal carcinomatosis was considered appropriate for primary cytoreduction after assessment of her thorax-abdominopelvic tomography, which revealed resectable intra-abdominal disease. Upon laparotomy, omental cake adherent to pelvis-filling mass, disseminated implants on the diaphragm, meso of the descending colon and small intestine were observed. The mass invaded the rectosigmoid colon, uterus, adnexa and the bladder resulting in frozen pelvis. Palpable retroperitoneal pelvic and para-aortic lymph nodes were detected. On the other side, stomach, anti-mesenteric surfaces and mesentery root of the small bowel were tumor-free. Hence, upon these perioperative and preoperative imaging findings, complete cytoreduction was thought to be achievable. Therefore, primary cytoreduction was performed. Total omentectomy, hysterectomy with bilateral salpingo-oophorectomy, rectosigmoid low anterior resection and retroperitoneal lymphadenectomy were performed. With the assistance of an injector needle connected to the insufflator tube (as in laparoscopic surgery), carbon dioxide gas was blown into the right retroperitoneal area and subsequently peritoneum was rapidly stripped up to the right diaphragm. The same procedure was then applied to the diaphragm and meso of the bowels, respectively. Owing to this technique, total stripping of all involved peritoneal surfaces was clearly facilitated and R0 goal was reached. Gas insufflation caused convenient detachment of the peritoneal surfaces along their

Deformation due to the distension of cylindrical igneous contacts: A kinematic model

NASA Astrophysics Data System (ADS)

Morgan, John

1980-06-01

A simple kinematic model is described that predicts the state of overall wall-rock strain resulting from the distension of igneous contacts. It applies to the axially symmetric expansion of any pluton whose overall shape is a cylinder with circular cross section i.e. to late magmatic plutons which are circular or annular in cross section. The model is not capable of predicting the strain distribution in the zone of contact strain, but does predict components of overall strain whose magnitudes are calculated from the change in shape of the zone of contact strain. These strain components are: (1) overall radial shortening of the wall rocks overlineer; (2) overall vertical extension overlineev; and (3) overall horizontal extension parallel to the contact overlineeh (the axis of symmetry is arbitrarily oriented vertically). In addition, one local strain magnitude can be predicted, namely the horizontal extension of the contact surface ehc. The four strain parameters and {(1 + overlineev) }/{(1 + overlineeh}) are graphed as functions of two independent variables: (1) outward distension of the contact ( r - r0)/ r; and (2) depth of contact strain ( rd - r)/ r. r is the present, observed radius of the pluton, r0 is the original radius and rd is the radius of contact strain. If ( rd- r)/ r is reduced or ( r - r0)/ r is increased, absolute values of the overall strain components are increased, ehc increases with ( r - r0)/ r but is independent of ( r d - r)/r · (1 + overlineev)/(l + overlineeh) ≅ 1 over a large range of values of both independent variables. The model has been applied to two Archean plutons in northwestern Ontario. According to a previous study, strain near the contact of the Bamaji-Blackstone batholith is characterized by large values of extension parallel to the contact and shortening normal to the contact, ( r - r0)/r and ( rd - r)/ r are estimated to be less than 0.20 and 0.27 respectively. The horizontal extension parallel to the contact is

Rapid and improved gas-liquid chromatography technique for detection of hippurate hydrolysis by Campylobacter jejuni and Campylobacter coli.

PubMed Central

Bär, W; Fricke, G

1987-01-01

A gas-liquid chromatographic method which requires no chloroform extraction of the split products has been investigated for the detection of hippurate hydrolysis by Campylobacter spp. This technique gave better reproducibility than other tests also used in this study and allows the routine use of the gas-liquid chromatographic method for identification of Campylobacter isolates. PMID:3654950

Lactobacillus farciminis treatment attenuates stress-induced overexpression of Fos protein in spinal and supraspinal sites after colorectal distension in rats.

PubMed

Ait-Belgnaoui, A; Eutamene, H; Houdeau, E; Bueno, L; Fioramonti, J; Theodorou, V

2009-05-01

Abstract Irritable bowel syndrome (IBS), frequently associated with psychological distress, is characterized by hypersensitivity to gut wall distension. Some probiotics are able to alleviate IBS symptoms and reduce visceromotor response to mechanical stimuli in animals. Moreover, we have previously shown that Lactobacillus farciminis treatment abolished the hyperalgesia to colorectal distension (CRD) induced by acute stress. The aims of the present study were to determine whether (i) stress-induced visceral hyperalgesia modifies the expression of Fos, a marker of general neuronal activation, induced by CRD, (ii) this activation can be modulated by L. farciminis treatment. Female rats were treated by L. farciminis and CRD was performed after partial restraint stress (PRS) or sham-PRS. The expression of Fos protein was measured by immunohistochemistry. After CRD or PRS, Fos expression was increased in spinal cord section (S1), nucleus tractus solitarius (NTS), paraventricular nucleus (PVN) of the hypothalamus, and in the medial nucleus of the amygdala (MeA). The combination of both stimuli, PRS and CRD, markedly increased this Fos overexpression in the sacral spinal cord section, PVN and MeA, but not in NTS. By contrast, a pretreatment with L. farciminis significantly reduced the number of Fos positive cells in these area. This study shows that PRS enhances Fos protein expression induced by CRD at the spinal and supraspinal levels in rats. Lactobacillus farciminis treatment inhibited this enhancing effect, suggesting that the antinociceptive effect of this probiotic strain results from a decrease of the stress-induced activation/sensitization of sensory neurons at the spinal and supraspinal level.

Application of Electromagnetic Induction Technique to Measure the Void Fraction in Oil/Gas Two Phase Flow

NASA Astrophysics Data System (ADS)

Wahhab, H. A. Abdul; Aziz, A. R. A.; Al-Kayiem, H. H.; Nasif, M. S.; Reda, M. N.

2018-03-01

In this work, electromagnetic induction technique of measuring void fraction in liquid/gas fuel flow was utilized. In order to improve the electric properties of liquid fuel, an iron oxide Fe3O4 nanoparticles at 3% was blended to enhance the liquid fuel magnetization. Experiments have been conducted for a wide range of liquid and gas superficial velocities. From the experimental results, it was realized that there is an existing linear relationship between the void fraction and the measured electromotive force, when induction coils were connected in series for excitation coils, regardless of increase or decrease CNG bubbles distribution in liquid fuel flow. Therefore, it was revealed that the utilized method yielded quite reasonable account for measuring the void fraction, showing good agreement with the other available measurement techniques in the two-phase flow, and also with the published literature of the bubbly flow pattern. From the results of the present investigation, it has been proven that the electromagnetic induction is a feasible technique for the actual measurement of void fraction in a Diesel/CNG fuel flow.

Smooth muscle in human bronchi is disposed to resist airway distension.

PubMed

Gazzola, Morgan; Henry, Cyndi; Couture, Christian; Marsolais, David; King, Gregory G; Fredberg, Jeffrey J; Bossé, Ynuk

2016-07-15

Studying airway smooth muscle (ASM) in conditions that emulate the in vivo environment within which the bronchi normally operate may provide important clues regarding its elusive physiological function. The present study examines the effect of lengthening and shortening of ASM on tension development in human bronchial segments. ASM from each bronchial segment was set at a length approximating in situ length (Linsitu). Bronchial tension was then measured during a slow cyclical strain (0.004Hz, from 0.7Linsitu to 1.3Linsitu) in the relaxed state and at graded levels of activation by methacholine. In all cases, tension was greater at longer ASM lengths, and greater during lengthening than shortening. The threshold of methacholine concentration that was required for ASM to account for bronchial tension across the entire range of ASM lengths tested was on average smaller by 2.8 logs during lengthening than during shortening. The length-dependency of ASM tension, together with this lower threshold of methacholine concentration during lengthening versus shortening, suggest that ASM has a greater ability to resist airway dilation during lung inflation than to narrow the airways during lung deflation. More than serving to narrow the airway, as has long been thought, these data suggest that the main function of ASM contraction is to limit airway wall distension during lung inflation. Copyright © 2016 Elsevier B.V. All rights reserved.

Duodenal afferent input converges onto T9-T10 spinal neurons responding to gastric distension in rats.

PubMed

Qin, Chao; Chen, Jiande D Z; Zhang, Jing; Foreman, Robert D

2007-12-01

Clinically, the overlap of gastroduodenal symptoms, such as visceral pain or hypersensitivity, is often observed in functional gastrointestinal disorders. The underlying mechanism may be related to intraspinal neuronal processing of noxious convergent inputs from the stomach and the intestine. The purpose of this study was to examine whether single low thoracic (T9-T10) spinal neurons responded to both gastric and duodenal mechanical stimulation. Extracellular potentials of single T9-T10 spinal neurons were recorded in pentobarbital anesthetized, paralyzed, and ventilated male rats. Graded gastric distensions (GD, 20, 40, 60 mm Hg, 20 s) were induced by air inflation of a latex balloon surgically placed in the stomach. Graded duodenal distensions (DD, 0.2, 0.4, 0.6 ml, 20 s) were produced by water inflation of a latex balloon placed into the duodenum. Of 70 deeper (depth from dorsal surface of spinal cord: 0.3-1.2 mm) spinal neurons responsive to noxious GD (> or =40 mm Hg), 44(63%) also responded to noxious DD (> or =0.4 ml). Similarly, 13/17 (76%) superficial neurons (depth <0.3 mm) responded to both GD and DD. Of 57 gastroduodenal convergent neurons, 41 (72%) had excitatory and 6 had inhibitory responses to both GD and DD; the remaining neurons exhibited multiple patterns of excitation and inhibition. 43/57 (75%) gastroduodenal convergent neurons had low-threshold (< or =20 mm Hg) responses to GD, whereas 42/57 (74%) of these neurons had high-threshold (> or =0.4 ml) responses to DD. In addition, 34/40 (85%) gastroduodenal convergent neurons had somatic receptive fields on the back, flank, and medial/lateral abdominal areas. These results suggested that superficial and deeper T9-T10 spinal neurons received innocuous and/or noxious convergent inputs from mechanical stimulation of the stomach and duodenum. Gastroduodenal convergent spinal neurons might contribute to intraspinal sensory transmission for cross-organ afferent-afferent communication between the

Hyperpolarized Gas MRI: Technique and Applications

PubMed Central

McAdams, Holman P.; Kaushik, S. Sivaram; Driehuys, Bastiaan

2015-01-01

Synopsis Functional imaging today offers a rich world of information that is more sensitive to changes in lung structure and function than traditionally obtained pulmonary function tests. Hyperpolarized helium (3He) and xenon (129Xe) MR imaging of the lungs provided new sensitive contrast mechanisms to probe changes in pulmonary ventilation, microstructure and gas exchange. With the recent scarcity in the supply of 3He the field of hyperpolarized gas imaging shifted to the use of cheaper and naturally available 129Xe. Xenon is well tolerated and recent technical advances have ensured that the 129Xe image quality is on par with that of 3He. The added advantage of 129Xe is its solubility in pulmonary tissue, which allows exploring specific lung function characteristics involved in gas exchange and alveolar oxygenation. With a plethora of contrast mechanisms, hyperpolarized gases and 129Xe in particular, stands to be an excellent probe of pulmonary structure and function, and provide sensitive and non-invasive biomarkers for a wide variety of pulmonary diseases. PMID:25952516

[Determination of acetanilide herbicide residues in tea by gas chromatography-mass spectrometry with two different ionization techniques].

PubMed

Shen, Weijian; Xu, Jinzhong; Yang, Wenquan; Shen, Chongyu; Zhao, Zengyun; Ding, Tao; Wu, Bin

2007-09-01

An analytical method of solid phase extraction-gas chromatography-mass spectrometry with two different ionization techniques was established for simultaneous determination of 12 acetanilide herbicide residues in tea-leaves. Herbicides were extracted from tea-leaf samples with ethyl acetate. The extract was cleaned-up on an active carbon SPE column connected to a Florisil SPE column. Analytical screening was determined by the technique of gas chromatography (GC)-mass spectrometry (MS) in the selected ion monitoring (SIM) mode with either electron impact ionization (EI) or negative chemical ionization (NCI). It is reliable and stable that the recoveries of all herbicides were in the range from 50% to 110% at three spiked levels, 10 microg/kg, 20 microg/kg and 40 microg/kg, and the relative standard deviations (RSDs) were no more than 10.9%. The two different ionization techniques are complementary as more ion fragmentation information can be obtained from the EI mode while more molecular ion information from the NCI mode. By comparison of the two techniques, the selectivity of NCI-SIM was much better than that of EI-SIM method. The sensitivities of the both techniques were high, the limit of quantitative (LOQ) for each herbicide was no more than 2.0 microg/kg, and the limit of detection (LOD) with NCI-SIM technique was much lower than that of EI-SIM when analyzing herbicides with several halogen atoms in the molecule.

A review on risk assessment techniques for hydraulic fracturing water and produced water management implemented in onshore unconventional oil and gas production.

PubMed

Torres, Luisa; Yadav, Om Prakash; Khan, Eakalak

2016-01-01

The objective of this paper is to review different risk assessment techniques applicable to onshore unconventional oil and gas production to determine the risks to water quantity and quality associated with hydraulic fracturing and produced water management. Water resources could be at risk without proper management of water, chemicals, and produced water. Previous risk assessments in the oil and gas industry were performed from an engineering perspective leaving aside important social factors. Different risk assessment methods and techniques are reviewed and summarized to select the most appropriate one to perform a holistic and integrated analysis of risks at every stage of the water life cycle. Constraints to performing risk assessment are identified including gaps in databases, which require more advanced techniques such as modeling. Discussions on each risk associated with water and produced water management, mitigation strategies, and future research direction are presented. Further research on risks in onshore unconventional oil and gas will benefit not only the U.S. but also other countries with shale oil and gas resources. Copyright © 2015 Elsevier B.V. All rights reserved.

[Development of a new technique to detect the laterality of microscopic hematuria by means of gas cystoscopy].

PubMed

Kamoi, K; Teraski, T; Kojima, M; Uchida, M; Watanabe, H

1996-04-01

We developed a new technique to determine the laterality of microscopic hematuria by means of gas cystoscopy. An originally designed catheter system consisted of two catheters. On the tip of an inner catheter, a urine dipstick for blood was attached, with a cap on the tip of an outer catheter to keep the dipstick dry. In order to react a dipstick with the urine coming out from a ureteral orifice in the bladder, CO2 was insufflated into the bladder through a cystoscope (gas cystoscopy). The laterality of microscopic hematuria was determined in the bladder, based on the color reaction on the dipstick. This technique was performed successfully in 14 (88%) of 16 cases with microscopic hematuria. The laterality of microscopic hematuria was determined to be ipsilateral in 6 patients, which coincided with the side of a urological upper urinary tract disorder. In contract, bilateral microscopic hematuria was confirmed in 8 patients with glomerular disorders. The diagnostic process in patients with microscopic hematuria remains unsolved for urologists and nephrologists. This technique may provide a new approach in diagnosing microscopic hematuria.

Systematic comparison of static and dynamic headspace sampling techniques for gas chromatography.

PubMed

Kremser, Andreas; Jochmann, Maik A; Schmidt, Torsten C

2016-09-01

Six automated, headspace-based sample preparation techniques were used to extract volatile analytes from water with the goal of establishing a systematic comparison between commonly available instrumental alternatives. To that end, these six techniques were used in conjunction with the same gas chromatography instrument for analysis of a common set of volatile organic carbon (VOC) analytes. The methods were thereby divided into three classes: static sampling (by syringe or loop), static enrichment (SPME and PAL SPME Arrow), and dynamic enrichment (ITEX and trap sampling). For PAL SPME Arrow, different sorption phase materials were also included in the evaluation. To enable an effective comparison, method detection limits (MDLs), relative standard deviations (RSDs), and extraction yields were determined and are discussed for all techniques. While static sampling techniques exhibited sufficient extraction yields (approx. 10-20 %) to be reliably used down to approx. 100 ng L(-1), enrichment techniques displayed extraction yields of up to 80 %, resulting in MDLs down to the picogram per liter range. RSDs for all techniques were below 27 %. The choice on one of the different instrumental modes of operation (aforementioned classes) was thereby the most influential parameter in terms of extraction yields and MDLs. Individual methods inside each class showed smaller deviations, and the least influences were observed when evaluating different sorption phase materials for the individual enrichment techniques. The option of selecting specialized sorption phase materials may, however, be more important when analyzing analytes with different properties such as high polarity or the capability of specific molecular interactions. Graphical Abstract PAL SPME Arrow during the extraction of volatile analytes from the headspace of an aqueous sample.

Modeling Respiratory Gas Dynamics in the Aviator’s Breathing System. Volume 2. Appendices

DTIC Science & Technology

1994-05-01

Rideout, at at. Dfference-Differentlat Equations for Fluid C... Flow in Distensible Tubes. IEEE Transactions on Bio-Medlcat C... Enginhering. Vot INE-14...McGraw-Hill; 1970; Chapter 13: 433-450. 12. Astrand, PO; Saltin, B. Oxygen uptake during the first minutes of heavy muscular exercise. J Appl Physiol...1802-1814; 1986. 233. Linehan, JH; Haworth, ST; Nelin, LD; Krenz, GS; Dawson, CA. A Simple Distensible Vessel Model for Interpreting Pulmonary

Velocity field measurement in gas-liquid metal two-phase flow with use of PIV and neutron radiography techniques.

PubMed

Saito, Y; Mishima, K; Tobita, Y; Suzuki, T; Matsubayashi, M

2004-10-01

To establish reasonable safety concepts for the realization of commercial liquid-metal fast breeder reactors, it is indispensable to demonstrate that the release of excessive energy due to re-criticality of molten core could be prevented even if a severe core damage accident took place. Two-phase flow due to the boiling of fuel-steel mixture in the molten core pool has a larger liquid-to-gas density ratio and higher surface tension in comparison with those of ordinary two-phase flows such as air-water flow. In this study, to investigate the effect of the recirculation flow on the bubble behavior, visualization and measurement of nitrogen gas-molten lead bismuth in a rectangular tank was performed by using neutron radiography and particle image velocimetry techniques. Measured flow parameters include flow regime, two-dimensional void distribution, and liquid velocity field in the tank. The present technique is applicable to the measurement of velocity fields and void fraction, and the basic characteristics of gas-liquid metal two-phase mixture were clarified.

Value of ¹⁸F-FDG PET/CT in the diagnosis of primary gastric cancer via stomach distension.

PubMed

Ma, Quanmei; Xin, Jun; Zhao, Zhoushe; Guo, Qiyong; Yu, Shupeng; Xu, Weina; Liu, Changping; Zhai, Wei

2013-06-01

To clarify the usefulness of (18)F-FDG PET/CT for detecting primary gastric cancer via gastric distention using a mixture of milk and Diatrizoate Meglumine. A total of 68 patients (male: 47, female: 21; age: 41-87 years) suspected of gastric carcinoma underwent (18)F-FDG PET/CT imaging. After whole-body PET/CT imaging in a fasting state, the patients drank a measured amount of milk with Diatrizoate Meglumine. Local gastric district PET/CT imaging was performed 30 min later. The imaging was analyzed by semi-quantitative analysis, standardized uptake value (SUV) of the primary tumor was measured in a region of interest. The diagnosis results were confirmed by gastroscopy, pathology, and follow-up results. Of the 68 patients, 56 malignant gastric neoplasm patients (male: 37, female: 19) were conformed. The sensitivity, specificity, positive predictive value and negative predictive value of fasting whole-body PET/CT imaging for a primary malignant tumor were 92.9%, 75.0%, 94.5%, and 69.0%, respectively. The values for distension with a mixture of milk and Diatrizoate Meglumine were 91.1%, 91.7%, 98.1%, and 68.8%, respectively. The area under the curve was 0.919 ± 0.033 and 0.883 ± 0.066 for the diagnosis of gastric cancer with SUVmax in a fasting state and after intake of mixture respectively, the differences were not statistically significant (P=0.359). Using gastric distension with a mixture of milk and Diatrizoate Meglumine, the mean ratio of the lesion's SUVmax to the adjacent gastric wall SUVmax increased significantly from 3.30 ± 3.05 to 13.50 ± 15.05, which was statistically significant (P<0.001). (18)F-FDG PET/CT imaging is highly accurate for the diagnosis of primary gastric carcinoma. Gastric distention can display the lesions more clearly, however, it cannot significantly improve diagnostic accuracy. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Reconnaissance techniques for determining soil-gas radon concentrations: an example from Prince Georges County, Maryland

USGS Publications Warehouse

Reimer, G.M.

1990-01-01

Radon reconnaissance requires some special considerations because a large area must be covered in a short period of time and analyses must be made soon after collection because of Rn decay. A simple approach to collection and field analysis consists of a small-diameter probe pounded into the ground to a depth of at least 0.75 m. Analysis is by an alpha-scintillometer. Soil-gas samples collected along a traverse in Prince Georges County, Maryland, demonstrates the utility of the technique. The reconnaissance sampling revealed Rn soil-gas concentrations of up to 2500 pCi/L (picocuries per liter) indicating that the potential exists for indoor accumulations in excess of 4 pCi/L. -from Author

The German collaborative project SUGAR Utilization of a natural treasure - Developing innovative techniques for the exploration and production of natural gas from hydrate-bearing sediments

NASA Astrophysics Data System (ADS)

Haeckel, M.; Bialas, J.; Wallmann, K. J.

2009-12-01

Gas hydrates occur in nature at all active and passive continental margins as well as in permafrost regions, and vast amounts of natural gas are bound in those deposits. Geologists estimate that twice as much carbon is bound in gas hydrates than in any other fossil fuel reservoir, such as gas, oil and coal. Hence, natural gas hydrates represent a huge potential energy resource that, in addition, could be utilized in a CO2-neutral and therefore environmentally friendly manner. However, the utilization of this natural treasure is not as easy as the conventional production of oil or natural gas and calls for new and innovative techniques. In the framework of the large-scale collaborative research project SUGAR (Submarine Deposits of Gas Hydrates - Exploration, Production and Transportation), we aim to produce gas from methane hydrates and to sequester carbon dioxide from power plants and other industrial sources as CO2 hydrates in the same host sediments. Thus, the SUGAR project addresses two of the most pressing and challenging topics of our time: development of alternative energy strategies and greenhouse gas mitigation techniques. The SUGAR project is funded by two federal German ministries and the German industry for an initial period of three years. In the framework of this project new technologies starting from gas hydrate exploration techniques over drilling technologies and innovative gas production methods to CO2 storage in gas hydrates and gas transportation technologies will be developed and tested. Beside the performance of experiments, numerical simulation studies will generate data regarding the methane production and CO2 sequestration in the natural environment. Reservoir modelling with respect to gas hydrate formation and development of migration pathways complete the project. This contribution will give detailed information about the planned project parts and first results with focus on the production methods.

Comparison of inert-gas-fusion and modified Kjeldahl techniques for determination of nitrogen in niobium alloys

NASA Technical Reports Server (NTRS)

Merkle, E. J.; Graab, J. W.; Davis, W. F.

1974-01-01

This report compares results obtained for the determination of nitrogen in a selected group of niobium-base alloys by the inert-gas-fusion and the Kjeldahl procedures. In the inert-gas-fusion procedure the sample is heated to approximately 2700 C in a helium atmosphere in a single-use graphite crucible. A platinum flux is used to facilitate melting of the sample. The Kjeldahl method consisted of a rapid decomposition with a mixture of hydrofluoric acid, phosphoric acid, and potassium chromate; distillation in the presence of sodium hydroxide; and highly sensitive spectrophotometry with nitroprusside-catalyzed indophenol. In the 30- to 80-ppm range, the relative standard deviation was 5 to 7 percent for the inert-gas-fusion procedure and 2 to 8 percent for the Kjeldahl procedure. The agreement of the nitrogen results obtained by the two techniques is considered satisfactory.

Simplified multiple headspace extraction gas chromatographic technique for determination of monomer solubility in water.

PubMed

Chai, X S; Schork, F J; DeCinque, Anthony

2005-04-08

This paper reports an improved headspace gas chromatographic (GC) technique for determination of monomer solubilities in water. The method is based on a multiple headspace extraction GC technique developed previously [X.S. Chai, Q.X. Hou, F.J. Schork, J. Appl. Polym. Sci., in press], but with the major modification in the method calibration technique. As a result, only a few iterations of headspace extraction and GC measurement are required, which avoids the "exhaustive" headspace extraction, and thus the experimental time for each analysis. For highly insoluble monomers, effort must be made to minimize adsorption in the headspace sampling channel, transportation conduit and capillary column by using higher operating temperature and a short capillary column in the headspace sampler and GC system. For highly water soluble monomers, a new calibration method is proposed. The combinations of these technique modifications results in a method that is simple, rapid and automated. While the current focus of the authors is on the determination of monomer solubility in aqueous solutions, the method should be applicable to determination of solubility of any organic in water.

Laser Frequency Stabilization for Coherent Lidar Applications using Novel All-Fiber Gas Reference Cell Fabrication Technique

NASA Technical Reports Server (NTRS)

Meras, Patrick, Jr.; Poberezhskiy, Ilya Y.; Chang, Daniel H.; Levin, Jason; Spiers, Gary D.

2008-01-01

Compact hollow-core photonic crystal fiber (HC-PCF)gas frequency reference cell was constructed using a novel packaging technique that relies on torch-sealing a quartz filling tube connected to a mechanical splice between regular and hollow-core fibers. The use of this gas cell for laser frequency stabilization was demonstrated by locking a tunable diode laser to the center of the P9 line from the (nu)1+(nu)3 band of acetylene with RMS frequency error of 2.06 MHz over 2 hours. This effort was performed in support of a task to miniaturize the laser frequency stabilization subsystem of JPL/LMCT Laser Absorption Spectrometer (LAS) instrument.

Gas-phase cationic benzoylation of ambient aromatic substrates studied with the decay technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Occhiucci, G.; Cacace, F.; Speranza, M.

1986-03-05

The gas-phase benzoylation of typical ambient aromatic substrates PhY (Y = OH, OMe, and NH/sub 2/) has been investigated by a combination of the decay technique and of FT ICR mass spectrometry. Labeled phenylium ions, C/sub 6/X/sub 5//sup +/ (X = H and T), from the decay of multiply tritiated benzene, C/sub 6/X/sub 6/, have been allowed to react with excess CO-containing traces of PhY (Y = OH, OMe, and NH/sub 2/), in the pressure range from 90 to 650 torr. Radio GLC and HPLC of the tritiated products demonstrate two competitive reaction channels, i.e., phenylation and benzoylation of themore » aromatic substrates. The results indicate a sharp kinetic bias of the gaseous phenylium ions for the aromatic substrates, measured by an apparent k/sub CO//k/sub PhY/ ratio of 0.12 (Y = OH), 0.13 (Y = OMe), and 0.04 (Y = NH/sub 2/) in the systems at nearly atmospheric pressure. Gas-phase benzoylation displays a high intramolecular selectivity, occurring exclusively at the n-type center of PhOH and PhNH/sub 2/. In the case of PhOMe, appreciable ring benzoylation is observed, characterized by a remarkably high (up to 30:1) bias for the para position. The mechanistic features of the gas-phase benzoylation and phenylation processes, deduced from the decay and the ICR experiments, are discussed and compared with those of related aromatic acylation and alkylation reactions occurring in the dilute gas state. 30 references, 2 tables.« less

Ventricular distension and diastolic coronary blood flow in the anaesthetized dog.

PubMed

Gattullo, D; Linden, R J; Losano, G; Pagliaro, P; Westerhof, N

1993-01-01

There appears to be no agreement as to whether or not an increase in diastolic left ventricular pressure and/or volume can cause a decrease in diastolic coronary blood flow. We investigated the problem in the anaesthetized dog using a flaccid freely distensible latex balloon inserted into the left ventricle with the animal on extracorporeal circulation and the coronary perfusion pressure constant at about 45 mm Hg. Maximal vasodilatation and suppression of autoregulation in coronary vasculature was obtained by the intracoronary infusion of dipyridamole (10-40 mg/h). Ventricular volume was changed in steps of 10 ml from 10 to 70 ml and back to 10 ml, whilst recording coronary blood flow and left ventricular pressure in the left circumflex coronary artery. Over a range of ventricular volumes from 20 to 50 ml and a concomitant rise in diastolic ventricular pressure to about 20 mm Hg there was no change in the diastolic coronary flow. Only when the ventricular volume was more than two times the control value (i.e. exceeded 50 ml) and left ventricular pressure was more than 20 mm Hg, was there a decrease in coronary flow. During the return of the volume to the control level there was a fall in diastolic flow and ventricular contractility with respect to the values obtained when the volume was increased; these two effects were transient lasting less than 10 min. It was not considered that any of the three models of the coronary circulation, waterfall, intramyocardial pump or varying elastance model could explain our results.(ABSTRACT TRUNCATED AT 250 WORDS)

Measuring trace gas emission from multi-distributed sources using vertical radial plume mapping (VRPM) and backward Lagrangian stochastic (bLS) techniques

USDA-ARS?s Scientific Manuscript database

Two micrometeorological techniques for measuring trace gas emission rates from distributed area sources were evaluated using a variety of synthetic area sources. The accuracy of the vertical radial plume mapping (VRPM) and the backward Lagrangian (bLS) techniques with an open-path optical spectrosco...

Standardized DMEK Technique: Reducing Complications Using Prestripped Tissue, Novel Glass Injector, and Sulfur Hexafluoride (SF6) Gas.

PubMed

Terry, Mark A; Straiko, Michael D; Veldman, Peter B; Talajic, Julia C; VanZyl, Cor; Sales, Christopher S; Mayko, Zachary M

2015-08-01

To report low complication rates in Descemet membrane endothelial keratoplasty (DMEK) using sulfur hexafluoride (SF6) gas, a novel glass injector, and donor tissue prestripped by an eye bank technician. A standardized technique of DMEK was performed in 80 consecutive Fuchs corneal dystrophy cases using technician-prestripped tissue, a novel glass injector, a modified Yoeruek tap technique, and an SF6 gas (20% concentration) bubble for prolonged tissue support. Twenty-five donors were premarked with an "S" stamp for intraoperative orientation. Surgery was performed by 2 experienced DMEK surgeons and 2 inexperienced cornea fellows. Complications were recorded, and the percent endothelial cell loss was calculated at 6 months postoperatively. There were 5 cases that received an air bubble injection postoperatively (6% rebubble rate). There were 6 grafts that immediately failed, 2 because of excessive surgical trauma, and 4 because of upside-down graft placement documented by optical coherence tomography. None of the 25 cases with an S stamp failed. Recipient corneas cleared quickly with no clinical evidence of toxicity from the SF6 gas bubble, and the grafts experienced a mean endothelial cell loss of 27% at 6 months. Tissue prestripped by an eye bank technician can be safely used for DMEK surgery. SF6 gas for prolonged tissue support may reduce the rebubble rate in DMEK, with no apparent acute toxic effect. An unrecognized upside-down graft was the primary cause of graft failure in this series. Upside-down grafts may be eliminated by the use of donor tissue premarked by the eye bank with an S orientation stamp.

Estimating the gas and dye quantities for modified tracer technique measurements of stream reaeration coefficients

USGS Publications Warehouse

Rathbun, R.E.

1979-01-01

Measuring the reaeration coefficient of a stream with a modified tracer technique has been accomplished by injecting either ethylene or ethylene and propane together and a rhodamine-WT dye solution into the stream. The movement of the tracers through the stream reach after injection is described by a one-dimensional diffusion equation. The peak concentrations of the tracers at the downstream end of the reach depend on the concentrations of the tracers in the stream at the injection site, the longitudinal dispersion coefficient, the mean water velocity, the length of the reach, and the duration of the injection period. The downstream gas concentrations also depend on the gas desorption coefficients of the reach. The concentrations of the tracer gases in the stream at the injection site depend on the flow rates of the gases through the injection diffusers, the efficiency of the gas absorption process, and the stream discharge. The concentration of dye in the stream at the injection site depends on the flow rate of the dye solution, the concentration of the dye solution, and the stream discharge. Equations for estimating the gas flow rates, the quantities of the gases, the dye concentration, and the quantity of dye together with procedures for determining the variables in these equations are presented. (Woodard-USGS)

Axial Movements and Length Changes of the Human Lower Esophageal Sphincter During Respiration and Distension-induced Secondary Peristalsis Using Functional Luminal Imaging Probe

PubMed Central

Liao, Donghua; Lottrup, Christian; Fynne, Lotte; McMahon, Barry P; Krogh, Klaus; Drewes, Asbjørn M; Zhao, Jingbo; Gregersen, Hans

2018-01-01

Background/Aims Efficient transport through the esophago-gastric junction (EGJ) requires synchronized circular and longitudinal muscle contraction of the esophagus including relaxation of the lower esophageal sphincter (LES). However, there is a scarcity of technology for measuring esophagus movements in the longitudinal (axial) direction. The aim of this study is to develop new analytical tools for dynamic evaluation of the length change and axial movement of the human LES based on the functional luminal imaging probe (FLIP) technology and to present normal signatures for the selected parameters. Methods Six healthy volunteers without hiatal hernia were included. Data were analyzed from stepwise LES distensions at 20, 30, and 40 mL bag volumes. The bag pressure and the diameter change were used for motion analysis in the LES. The cyclic bag pressure frequency was used to distinguish dynamic changes of the LES induced by respiration and secondary peristalsis. Results Cyclic fluctuations of the LES were evoked by respiration and isovolumetric distension, with phasic changes of bag pressure, diameter, length, and axial movement of the LES narrow zone. Compared to the respiration-induced LES fluctuations, peristaltic contractions increased the contraction pressure amplitude (P < 0.001), shortening (P < 0.001), axial movement (P < 0.001), and diameter change (P < 0.01) of the narrow zone. The length of the narrow zone shortened as function of the pressure increase. Conclusions FLIP can be used for evaluation of dynamic length changes and axial movement of the human LES. The method may shed light on abnormal longitudinal muscle activity in esophageal disorders. PMID:29605981

CdS QDs-chitosan microcapsules with stimuli-responsive property generated by gas-liquid microfluidic technique.

PubMed

Chen, Yanjun; Yao, Rongyi; Wang, Yifeng; Chen, Ming; Qiu, Tong; Zhang, Chaocan

2015-01-01

This article describes a straightforward gas-liquid microfluidic approach to generate uniform-sized chitosan microcapsules containing CdS quantum dots (QDs). CdS QDs are encapsulated into the liquid-core of the microcapsules. The sizes of the microcapsules can be conveniently controlled by gas flow rate. QDs-chitosan microcapsules show good fluorescent stability in water, and exhibit fluorescent responses to chemical environmental stimuli. α-Cyclodextrin (α-CD) causes the microcapsules to deform and even collapse. More interestingly, α-CD induces obvious changes on the fluorescent color of the microcapsules. However, β-cyclodextrin (β-CD) has little influence on the shape and fluorescent color of the microcapsules. Based on the results of scanning electron microscopy, the possible mechanism about the effects of α-CD on the chitosan microcapsules is analyzed. These stimuli-responsive microcapsules are low-cost and easy to be prepared by gas-liquid microfluidic technique, and can be applied as a potential micro-detector to chemicals, such as CDs. Copyright © 2014 Elsevier B.V. All rights reserved.

Both exogenous 5-HT and endogenous 5-HT, released by fluoxetine, enhance distension evoked propulsion in guinea-pig ileum in vitro.

PubMed

Gwynne, Rachel M; Clarke, Amanda J; Furness, John B; Bornstein, Joel C

2014-01-01

The roles of 5-HT3 and 5-HT4 receptors in the modulation of intestinal propulsion by luminal application of 5-HT and augmentation of endogenous 5-HT effects were studied in segments of guinea-pig ileum in vitro. Persistent propulsive contractions evoked by saline distension were examined using a modified Trendelenburg method. When 5-HT (30 nM), fluoxetine (selective serotonin reuptake inhibitor; 1 nM), 2-methyl-5-HT (5-HT3 receptor agonist; 1 mM), or RS 67506 (5-HT4 receptor agonist, 1 μM) was infused into the lumen, the pressure needed to initiate persistent propulsive activity fell significantly. A specific 5-HT4 receptor antagonist, SB 207266 (10 nM in lumen), abolished the effects of 5-HT, fluoxetine, and RS 67506, but not those of 2-methyl-5-HT. Granisetron (5-HT3 receptor antagonist; 1 μM in lumen) abolished the effect of 5-HT, fluoxetine, RS 67506, and 2-methyl-5-HT. The NK3 receptor antagonist SR 142801 (100 nM in lumen) blocked the effects of 5-HT, fluoxetine, and 2-methyl-5-HT. SB 207266, granisetron, and SR 142801 had no effect by themselves. Higher concentrations of fluoxetine (100 and 300 nM) and RS 67506 (3 and 10 μM) had no effect on the distension threshold for propulsive contractions. These results indicate that luminal application of exogenous 5-HT, or increased release of endogenous mucosal 5-HT above basal levels, acts to lower the threshold for propulsive contractions in the guinea-pig ileum via activation of 5-HT3 and 5-HT4 receptors and the release of tachykinins. The results further indicate that basal release of 5-HT is insufficient to alter the threshold for propulsive motor activity.

Adaptation of the rumen microbial population to native potato starch degradation determined with the gas production technique and the nylon bag technique.

PubMed

Cone, J W; van Gelder, A H

2006-12-01

Experiments were conducted to investigate the influence of the adaptation of rumen micro-organisms on the degradation of native potato starch (PS) in the rumen. Cows were fed with rations used for gas production (GP) analysis (dry cows, 1.6% starch) and for the nylon bag (NB) technique (lactating cows, 23% starch, mainly maize starch) and a ration containing 19% native PS (lactating cows). Fermentation characteristics of 13 samples were investigated with the GP technique using rumen fluid from cows fed each of the three rations. The same samples were investigated with the NB technique in the cows obtaining the NB ration and the PS ration. The results showed that the rate of GP was influenced by the source of the rumen fluid. The fermentation rate of PS was considerably enhanced by using rumen fluid adapted to the fermentation of native PS instead of using the other rumen fluids. Incubating in cows fed the PS ration, the rate of PS degradation determined with the NB technique, was higher compared with cows fed other rations. Using the PS ration the observed lag period for PS was shorter. The results show a clear influence of ration on the degradation characteristics of starch, determined with both the GP technique and the NB technique. However, these changes in behaviour did not explain observed differences in amounts of rumen escape PS measured in vivo in animal experiments and in situ, using the NB technique.

Gas insufflation of minimal preparation CT of the colon reduces false-positives

PubMed Central

Slater, A; North, M; Hart, M; Ferrett, C

2012-01-01

Objectives Minimal preparation CT of the colon (MPCT colon) is used for investigation of suspected colorectal cancer in frail and/or elderly patients who would be expected to tolerate laxative bowel preparation poorly. Although it has good sensitivity for colorectal cancer it has a poor specificity. We wished to investigate whether distension of the colon with carbon dioxide alone would reduce the number of false-positives, but without making the test arduous or excessively uncomfortable. Methods 134 patients were recruited and underwent MPCT colon with gas insufflation and antispasmodics. Results were compared with a cohort of 134 patients undergoing standard protocol MPCT colon. The numbers of false-positives were compared, as was reader confidence. All trial patients were given a questionnaire documenting their experience. Results The number of false-positives was 15% in the control group and 5% in the trial group; this difference was statistically significant, (p=0.01). Reader confidence was increased in the trial group. Patient tolerance was good, with 95% saying they would have the test again. Conclusion Use of gas insufflation and antispasmodics reduces the false-positives from 15% to 5% without adversely affecting patient tolerance. PMID:21224295

Advanced Laser-Based Techniques for Gas-Phase Diagnostics in Combustion and Aerospace Engineering.

PubMed

Ehn, Andreas; Zhu, Jiajian; Li, Xuesong; Kiefer, Johannes

2017-03-01

Gaining information of species, temperature, and velocity distributions in turbulent combustion and high-speed reactive flows is challenging, particularly for conducting measurements without influencing the experimental object itself. The use of optical and spectroscopic techniques, and in particular laser-based diagnostics, has shown outstanding abilities for performing non-intrusive in situ diagnostics. The development of instrumentation, such as robust lasers with high pulse energy, ultra-short pulse duration, and high repetition rate along with digitized cameras exhibiting high sensitivity, large dynamic range, and frame rates on the order of MHz, has opened up for temporally and spatially resolved volumetric measurements of extreme dynamics and complexities. The aim of this article is to present selected important laser-based techniques for gas-phase diagnostics focusing on their applications in combustion and aerospace engineering. Applicable laser-based techniques for investigations of turbulent flows and combustion such as planar laser-induced fluorescence, Raman and Rayleigh scattering, coherent anti-Stokes Raman scattering, laser-induced grating scattering, particle image velocimetry, laser Doppler anemometry, and tomographic imaging are reviewed and described with some background physics. In addition, demands on instrumentation are further discussed to give insight in the possibilities that are offered by laser flow diagnostics.

Aspects of rf-heating and gas-phase doping of large scale silicon crystals grown by the Float Zone technique

NASA Astrophysics Data System (ADS)

Zobel, F.; Mosel, F.; Sørensen, J.; Dold, P.

2018-05-01

Float Zone growth of silicon crystals is known as the method for providing excellent material properties. Basic principle of this technique is the radiofrequency induction heating, main aspects of this method will be discussed in this article. In contrast to other methods, one of the advantages of the Float Zone technique is the possibility for in-situ doping via gas phase. Experimental results on this topic will be shown and discussed.

Comparison of the gas-liquid dual support fixation and Heitzman fixation techniques for preparing lung specimens

PubMed Central

Yu, Dongsheng; Qu, Weili; Xia, Haipeng; Li, Xiaofeng; Luan, Zhenfeng; Yan, Renjie; Lu, Xiaodong; Zhao, Peng

2017-01-01

The aim of the present study was to compare the gas-liquid dual support fixation and Heitzman fixation techniques for the preparation of lung specimens. A total of 40 fresh lung samples were surgically collected from 40 male patients with lung cancer by biopsy. Patients were recruited from the Affiliated Hospital of Qingdao University Medical College (Qingdao, China) between July 2007 and June 2014. Samples were prepared using either the gas-liquid dual support fixation method (group A; n=26) or the Heitzman fixation method (group B; n=14). High-resolution computed tomography (HRCT) scanning was performed prior to surgery and corresponding postoperative HRCT scanning was conducted for the lung specimens; the gross transverse specimen section, cord photography images and histological sections were evaluated. Morphological observations of lung specimens indicated that there were 22 cases in group A with grade I (84.6%) and 4 cases with grade II (15.4%), whereas, in group B, there were 5 cases with grade II (35.7%) and 9 cases with grade III (64.3%). Statistical analysis demonstrated that the grades of specimens between the two groups were significantly different (P<0.01). Results from imaging and histological studies found that the quality of lung specimens was superior in group A, compared with group B. In conclusion, the present study demonstrated that, compared with the Heitzman fixation method, gas-liquid dual support fixation may be a superior technique for the preparation of lung specimens. This finding may facilitate the improvement of lung HRCT and pathological studies. PMID:28673006

Comparison of the gas-liquid dual support fixation and Heitzman fixation techniques for preparing lung specimens.

PubMed

Yu, Dongsheng; Qu, Weili; Xia, Haipeng; Li, Xiaofeng; Luan, Zhenfeng; Yan, Renjie; Lu, Xiaodong; Zhao, Peng

2017-07-01

The aim of the present study was to compare the gas-liquid dual support fixation and Heitzman fixation techniques for the preparation of lung specimens. A total of 40 fresh lung samples were surgically collected from 40 male patients with lung cancer by biopsy. Patients were recruited from the Affiliated Hospital of Qingdao University Medical College (Qingdao, China) between July 2007 and June 2014. Samples were prepared using either the gas-liquid dual support fixation method (group A; n=26) or the Heitzman fixation method (group B; n=14). High-resolution computed tomography (HRCT) scanning was performed prior to surgery and corresponding postoperative HRCT scanning was conducted for the lung specimens; the gross transverse specimen section, cord photography images and histological sections were evaluated. Morphological observations of lung specimens indicated that there were 22 cases in group A with grade I (84.6%) and 4 cases with grade II (15.4%), whereas, in group B, there were 5 cases with grade II (35.7%) and 9 cases with grade III (64.3%). Statistical analysis demonstrated that the grades of specimens between the two groups were significantly different (P<0.01). Results from imaging and histological studies found that the quality of lung specimens was superior in group A, compared with group B. In conclusion, the present study demonstrated that, compared with the Heitzman fixation method, gas-liquid dual support fixation may be a superior technique for the preparation of lung specimens. This finding may facilitate the improvement of lung HRCT and pathological studies.

Radioactive-gas separation technique

NASA Technical Reports Server (NTRS)

Haney, R.; King, K. J.; Nellis, D. O.; Nisson, R. S.; Robling, P.; Womack, W.

1977-01-01

Cryogenic technique recovers gases inexpensively. Method uses differences in vapor pressures, melting points, and boiling points of components in gaseous mixture. Series of temperature and pressure variations converts gases independently to solid and liquid states, thereby simplifying separation. Apparatus uses readily available cryogen and does not require expensive refrigeration equipment.

Planar Zeolite Film-Based Potentiometric Gas Sensors Manufactured by a Combined Thick-Film and Electroplating Technique

PubMed Central

Marr, Isabella; Reiß, Sebastian; Hagen, Gunter; Moos, Ralf

2011-01-01

Zeolites are promising materials in the field of gas sensors. In this technology-oriented paper, a planar setup for potentiometric hydrocarbon and hydrogen gas sensors using zeolites as ionic sodium conductors is presented, in which the Pt-loaded Na-ZSM-5 zeolite is applied using a thick-film technique between two interdigitated gold electrodes and one of them is selectively covered for the first time by an electroplated chromium oxide film. The influence of the sensor temperature, the type of hydrocarbons, the zeolite film thickness, and the chromium oxide film thickness is investigated. The influence of the zeolite on the sensor response is briefly discussed in the light of studies dealing with zeolites as selectivity-enhancing cover layers. PMID:22164042

Gel instillation sonohysterography (GIS) and saline contrast sonohysterography (SCSH): comparison of two diagnostic techniques.

PubMed

Bij de Vaate, A J M; Brölmann, H A M; van der Slikke, J W; Emanuel, M H; Huirne, J A F

2010-04-01

To compare gel instillation sonohysterography (GIS) with saline contrast sonohysterography (SCSH) as diagnostic methods for the evaluation of the uterine cavity. A prospective cohort study was performed at the Department of Obstetrics and Gynecology of the VU University Medical Center, Amsterdam, between September 2007 and April 2008. We included 65 women suspected of having an intrauterine abnormality with an indication for SCSH/GIS. First SCSH and subsequently GIS were performed in all women. Distension of the uterine cavity, image quality, visualization of intrauterine abnormalities and pain experienced on a visual analog scale (VAS score) were recorded for both procedures. The mean distension with GIS was 9.0 mm and with SCSH it was 8.5 mm (P = 0.15). The mean image quality, on a scale from 0 to 5, for SCSH was 4.0 and for GIS it was 3.6 (P = 0.01). No difference was found for the visualization of intrauterine abnormalities, and the VAS scores for pain experienced on SCSH and GIS were 1.5 and 1.6, respectively (P = 0.62). The image quality of SCSH is slightly better than that of GIS. This difference is likely to be attributable to the presence of air bubbles in the gel. The small difference in uterine cavity distension in favor of GIS and comparable stable distension during at least 4 min make GIS a suitable alternative for SCSH if air bubbles can be prevented. Copyright 2009 ISUOG. Published by John Wiley & Sons, Ltd.

Relation of Sex Hormone Levels With Prevalent and 10-Year Change in Aortic Distensibility Assessed by MRI: The Multi-Ethnic Study of Atherosclerosis.

PubMed

Subramanya, Vinita; Ambale-Venkatesh, Bharath; Ohyama, Yoshiaki; Zhao, Di; Nwabuo, Chike C; Post, Wendy S; Guallar, Eliseo; Ouyang, Pamela; Shah, Sanjiv J; Allison, Matthew A; Ndumele, Chiadi E; Vaidya, Dhananjay; Bluemke, David A; Lima, Joao A; Michos, Erin D

2018-06-11

Women experience a steeper decline in aortic elasticity related to aging compared to men. We examined whether sex hormone levels were associated with ascending aortic distensibility (AAD) in the Multi-Ethnic Study of Atherosclerosis. We studied 1,345 postmenopausal women and 1,532 men aged 45-84 years, who had serum sex hormone levels, AAD measured by phase-contrast cardiac magnetic resonance imaging, and ejection fraction>50% at baseline. Among these participants, 457 women and 548 men returned for follow-up magnetic resonance imaging 10-years later. Stratified by sex, and using mixed effects linear regression methods, we examined associations of sex hormones (as tertiles) with baseline and annual change in log-transformed AAD (mm Hg-110-3), adjusting for demographics, body size, lifestyle factors, mean arterial pressure, heart rate, hypertensive medication use (and in women, for hormone therapy use and years since menopause). The mean (SD) age was 65 (9) for women and 62 (10) years for men. AAD was lower in women than men (P < 0.001). In adjusted cross-sectional analysis, the highest tertile of free testosterone (compared to lowest) in women was significantly associated with lower AAD [-0.10 (-0.19, -0.01)] and the highest tertile of estradiol in men was associated with greater AAD [0.12 (0.04, 0.20)]. There were no associations of sex hormones with change in AAD over 10 years, albeit in a smaller sample size. Lower free testosterone in women and higher estradiol in men were associated with greater aortic distensibility at baseline, but not longitudinally. Sex hormone levels may account for differences in AAD between women and men.

Slip length measurement of gas flow.

PubMed

Maali, Abdelhamid; Colin, Stéphane; Bhushan, Bharat

2016-09-16

In this paper, we present a review of the most important techniques used to measure the slip length of gas flow on isothermal surfaces. First, we present the famous Millikan experiment and then the rotating cylinder and spinning rotor gauge methods. Then, we describe the gas flow rate experiment, which is the most widely used technique to probe a confined gas and measure the slip. Finally, we present a promising technique using an atomic force microscope introduced recently to study the behavior of nanoscale confined gas.

Biliary access in technically difficult biliary cannulation: the mucosal bridge technique

PubMed Central

Thomas, Rebecca; Shah, Suhaila Rizal; Worthley, Christopher S

2009-01-01

Background: The use of precut sphincterotomy during endoscopic retrograde cholangiopancreatography (ERCP) facilitates selective bile duct access in difficult procedures. However, it is also associated with high rates of complications. Several techniques for precut sphincterotomy have been described in the literature. This paper reports our experience with a non-needle-knife technique for precut sphincterotomy, namely, the mucosal bridge technique. Methods: We analysed the experience of a single surgical endoscopist at our centre in performing precut sphincterotomies by retrospectively examining information in the database for January 2002 to February 2008, which had been stored prospectively using Endoscribe. Results: The mucosal bridge technique was performed in 16 (3.19%) of 501 patients. Success rates were 75% and 100% after first and second ERCPs, respectively. The failure of initial procedures was caused by bleeding, tissue oedema, poorly visualized papilla or a poorly distensible duodenum and oedematous papilla. There were four cases of complications, which included periductular extravasation of contrast, bleeding, and sepsis in two patients. However, these complications were not a direct consequence of the precut sphincterotomy. Conclusions: The mucosal bridge technique can be used to increase the likelihood of successful bile duct cannulation, thus preventing the need for a second intervention. PMID:19590645

X-ray absorption and Mössbauer spectroscopies characterization of iron nanoclusters prepared by the gas aggregation technique.

PubMed

Sánchez-Marcos, J; Laguna-Marco, M A; Martínez-Morillas, R; Céspedes, E; Menéndez, N; Jiménez-Villacorta, F; Prieto, C

2012-11-01

Partially oxidized iron nanoclusters have been prepared by the gas-phase aggregation technique with typical sizes of 2-3 nm. This preparation technique has been reported to obtain clusters with interesting magnetic properties such as very large exchange bias. In this paper, a sample composition study carried out by Mössbauer and X-ray absorption spectroscopies is reported. The information reached by these techniques, which is based on the iron short range order, results to be an ideal way to have a characterization of the whole sample since the obtained data are an average over a very large amount of the clusters. In addition, our results indicate the presence of ferrihydrite, which is a compound typically ignored when studying this type of systems.

Estimation of VOC emissions from produced-water treatment ponds in Uintah Basin oil and gas field using modeling techniques

NASA Astrophysics Data System (ADS)

Tran, H.; Mansfield, M. L.; Lyman, S. N.; O'Neil, T.; Jones, C. P.

2015-12-01

Emissions from produced-water treatment ponds are poorly characterized sources in oil and gas emission inventories that play a critical role in studying elevated winter ozone events in the Uintah Basin, Utah, U.S. Information gaps include un-quantified amounts and compositions of gases emitted from these facilities. The emitted gases are often known as volatile organic compounds (VOCs) which, beside nitrogen oxides (NOX), are major precursors for ozone formation in the near-surface layer. Field measurement campaigns using the flux-chamber technique have been performed to measure VOC emissions from a limited number of produced water ponds in the Uintah Basin of eastern Utah. Although the flux chamber provides accurate measurements at the point of sampling, it covers just a limited area of the ponds and is prone to altering environmental conditions (e.g., temperature, pressure). This fact raises the need to validate flux chamber measurements. In this study, we apply an inverse-dispersion modeling technique with evacuated canister sampling to validate the flux-chamber measurements. This modeling technique applies an initial and arbitrary emission rate to estimate pollutant concentrations at pre-defined receptors, and adjusts the emission rate until the estimated pollutant concentrations approximates measured concentrations at the receptors. The derived emission rates are then compared with flux-chamber measurements and differences are analyzed. Additionally, we investigate the applicability of the WATER9 wastewater emission model for the estimation of VOC emissions from produced-water ponds in the Uintah Basin. WATER9 estimates the emission of each gas based on properties of the gas, its concentration in the waste water, and the characteristics of the influent and treatment units. Results of VOC emission estimations using inverse-dispersion and WATER9 modeling techniques will be reported.

The Intestinal Gas Questionnaire: development of a new instrument for measuring gas-related symptoms and their impact on daily life.

PubMed

Chassany, O; Tugaut, B; Marrel, A; Guyonnet, D; Arbuckle, R; Duracinsky, M; Whorwell, P J; Azpiroz, F

2015-06-01

Although gas-related symptoms (GRS) are common and intrusive, there are no questionnaires to quantitate this problem. This study aimed to develop an instrument to rectify this gap in our knowledge. Concepts were initially identified from the literature and interviews with gastroenterologists. Exploratory one-to-one interviews and focus groups with irritable bowel syndrome (IBS) patients (n = 28) and non-IBS subjects (n = 27) with GRS were conducted in UK, France, and Spain leading to a conceptual framework for the questionnaire. Last, iterative rounds of cognitive debriefing were performed with IBS (n = 16) and non-IBS subjects (n = 14). From the first three steps, nine GRS (bloating, distension, flatulence, odorous flatulence, difficult gas evacuation, stomach rumbling, belching, bad breath, and abdominal movement) were identified although abdominal movement was subsequently excluded. Twelve quality of life domains affected by these symptoms were identified as: Clothing, emotional, physical appearance, diet, daily living, work, social life, physical activity, relationships, sex life, sleep, and cognitive function. A 24-h recall for symptoms and a 7-day recall for impact assessment were supported by the qualitative findings. Cognitive debriefing confirmed the understanding of the instrument. Across the three languages, the instrument was conceptually and linguistically consistent. The International Gas Questionnaire is a 2-part instrument, developed rigorously and simultaneously in three languages assessing seven symptoms (17 items) and their impact on 12 domains (26 items) in IBS and general population. It is now undergoing psychometric validation and should provide a unique tool for epidemiological surveys and clinical trials for developing new treatments for these symptoms. © 2015 John Wiley & Sons Ltd.

Pulmonary arterial distension and vagal afferent nerve activity in anaesthetized dogs.

PubMed

Moore, Jonathan P; Hainsworth, Roger; Drinkhill, Mark J

2004-03-16

Distension of the main pulmonary artery and its bifurcation are known to result in a reflex vasoconstriction and increased respiratory drive; however, these responses are observed at abnormally high distending pressures. In this study we recorded afferent activity from pulmonary arterial baroreceptors to investigate their stimulus-response characteristics and to determine whether they are influenced by physiological changes in intrathoracic pressure. In chloralose-anaesthetized dogs, a cardiopulmonary bypass was established, the pulmonary trunk and its main branches were vascularly isolated and perfused with venous blood at pulsatile pressures designed to simulate the normal pulmonary arterial pressure waveform. Afferent slips of a cervical vagus were dissected and nerve fibres identified that displayed discharge patterns with characteristics expected from pulmonary arterial baroreceptors. Recordings were obtained with (a) chest open (b) chest closed and resealed, and (c) with phasic negative intrathoracic pressures in the resealed chest. Pressure-discharge characteristics obtained in the open-chest animals indicated that the threshold pulmonary pressure (corresponding to 5% of the overall response) was 17.1 +/- 2.9 and the inflexion point of the curve was 29.2 +/- 3.3 mmHg (mean +/-S.E.M). In closed-chest animals the threshold and inflexion pressures were reduced to 12.0 +/- 1.7 and 20.7 +/- 1.8 mmHg. Application of phasic negative intrathoracic pressures further reduced the threshold and inflexion pressures to 9.5 +/- 1.2 mmHg (P < 0.05 vs. open) and 14.7 +/- 0.8 mmHg (P < 0.003 vs. open and P < 0.02 vs. atmospheric). These results indicate that under physiological conditions, with closed-chest and phasic negative intrathoracic pressure changes similar to those associated with normal breathing, activity from pulmonary baroreceptors is obtained at physiological pulmonary arterial pressures in intact animals.

Applications of the pulsed gas stripper technique at the GSI UNILAC

NASA Astrophysics Data System (ADS)

Scharrer, P.; Barth, W.; Bevcic, M.; Düllmann, Ch. E.; Gerhard, P.; Groening, L.; Horn, K. P.; Jäger, E.; Khuyagbaatar, J.; Krier, J.; Vormann, H.; Yakushev, A.

2017-08-01

In the frame of an upgrade program for the GSI UNILAC, preparing it for the use as an injector system for FAIR, a pulsed gas stripper cell was developed. It utilizes the required low duty cycle by applying a pulsed gas injection instead of a continuous gas inlet. The resulting lower gas consumption rate enables the use of low-Z gas targets over a wide range of stripper target thicknesses. The setup enables an increased flexibility for the accelerator by allowing the gas stripper to be used in time-sharing beam operation matching the capabilities of the GSI UNILAC like the acceleration of different ion beams in quasi-parallel operation. Measured charge state distributions of 238U, 50Ti, and CH3 beams on H2 and N2 gas highlight the benefits of the pulsed gas stripper cell for the accelerator operation and performance.

Gas Chromatography.

ERIC Educational Resources Information Center

Karasek, Francis W.; And Others

1984-01-01

This review covers fundamental developments in gas chromatography during 1982 and 1983. Literature is considered under these headings: columns; liguid phases; solid supports; sorption processes and solvents; open tubular column gas chromatography; instrumentation; high-resolution columns and applications; other techniques; qualitative and…

Thermal, optical and gas sensing properties of ZnO films prepared by different techniques

NASA Astrophysics Data System (ADS)

Bhatia, Sonik; Verma, Neha; Aggarwal, Munish

2018-03-01

Nowadays, for environmental protection, the use of portable gas sensor is essential to detect toxic gases. To control this problem of hazardous gases, metal oxide based sensors plays a vital role. In this recent study, Indium (2 at.wt.%) doped ZnO films has been prepared by sol gel spin coating and thermal evaporation techniques on glass substrates. To enhance the sensing properties, indium (In) was used as dopant and their annealing effect of temperature was observed. Thermal properties have shown the fruitful result that prepared films are useful for the fabrication of solar cell. Electrical properties revealed that capacitance and dielectric constant decreases with increase in frequency. X-ray Diffraction showed hexagonal wurtzite structure highly oriented along (1 0 1) plane. Field emission scanning electron microscope of these synthesis films prepared by different have shown the morphology as nanospheres having size of the order of 40-60 nm. 2.0 at.% of indium as modifier resulted in highest response and selectivity towards 5 ppm of NO2 gas at different operating temperature (50-200 °C). Highest sensitivity was obtained at operating temperature of 150 °C. Prepared films have quick response and recovery time in the range of 14-27 s and 67-63 s. The highest response and recovery time of gas sensor was explained by valence ion mechanism.

Studying gas-sheared liquid film in horizontal rectangular duct with laser-induced fluorescence technique

NASA Astrophysics Data System (ADS)

Cherdantsev, Andrey; Hann, David; Azzopardi, Barry

2013-11-01

High-speed LIF-technique is applied to study gas-sheared liquid film in horizontal rectangular duct with 161 mm width. Instantaneous distributions of film thickness resolved in both longitudinal and transverse coordinates were obtained with a frequency of 10 kHz and spatial resolution from 0.125 mm to 0.04 mm. Processes of generation of fast and slow ripples by disturbance waves are the same as described in literature for downwards annular pipe flow. Disturbance waves are often localized by transverse coordinate and may have curved or slanted fronts. Fast ripples, covering disturbance waves, are typically horseshoe-shaped and placed in staggered order. Their characteristic transverse size is of order 1 cm and it decreases with gas velocity. Entrainment of liquid from film surface can also be visualized. Mechanisms of ripple disruption, known as ``bag break-up'' and ``ligament break-up,'' were observed. Both mechanisms may occur on the same disturbance waves. Various scenarios of droplet deposition on the liquid film are observed, including the impact, slow sinking and bouncing, characterized by different outcome of secondary droplets or entrapped bubbles. Number and size of bubbles increase greatly inside the disturbance waves. Both quantities increase with gas and liquid flow rates. EPSRC Programme Grant MEMPHIS (EP/K003976/1), and Roll-Royce UTC (Nottingham, for access to flow facility).

Neuroanatomic and behavioral correlates of urinary dysfunction induced by vaginal distension in rats.

PubMed

Palacios, J L; Juárez, M; Morán, C; Xelhuantzi, N; Damaser, M S; Cruz, Y

2016-05-01

The aim of the present study was to use a model of simulated human childbirth in rats to determine the damage to genitourinary structures and behavioral signs of urinary dysfunction induced by vaginal distension (VD) in female rats. In experiment 1, the length of the genitourinary tract and the nerves associated with it were measured immediately after simulated human delivery induced by VD or sham (SH) procedures. Electroneurograms of the dorsal nerve of the clitoris (DNC) were also recorded. In experiment 2, histological characteristics of the bladder and major pelvic ganglion of VD and SH rats were evaluated. In experiment 3, urinary parameters were determined in conscious animals during 6 h of dark and 6 h of light before and 3 days after VD or SH procedures. VD significantly increased distal vagina width (P < 0.001) and the length of the motor branch of the sacral plexus (P < 0.05), DNC (P < 0.05), and vesical nerves (P < 0.01) and decreased DNC frequency and amplitude of firing. VD occluded the pelvic urethra, inducing urinary retention, hematomas in the bladder, and thinness of the epithelial (P < 0.05) and detrusor (P < 0.01) layers of the bladder. Major pelvic ganglion parameters were not modified after VD. Rats dripped urine in unusual places to void, without the stereotyped behavior of micturition after VD. The neuroanatomic injuries after VD occur alongside behavioral signs of urinary incontinence as determined by a new behavioral tool for assessing micturition in conscious animals.

Relationship of Aortic Wall Distensibility to Mitral and Aortic Valve Calcification: The Multi-Ethnic Study of Atherosclerosis.

PubMed

Cohoon, Kevin P; Criqui, Michael H; Budoff, Matthew J; Lima, Joao A; Blaha, Michael J; Decker, Paul A; Durazo, Ramon; Liu, Kiang; Kramer, Holly

2018-05-01

Data are limited on whether valvular calcification is associated with aortic wall stiffness. We tested whether aortic valve calcification (AVC) and/or mitral valve calcification (MVC) is inversely associated with aortic distensibility (AD). Cross-sectional study conducted in a subset of the Multi-Ethnic Study of Atherosclerosis (MESA) included 3676 MESA participants aged 44 to 84 years with AD measured with magnetic resonance imaging and with AVC and MVC measured with noncontrast cardiac computed tomography scans. Both AVC and MVC were divided into 3 categories: zero, < median values (low), and ≥ median values (high) for patients with nonzero values. Overall, 88% (n = 3256) and 92% (n = 3365) of participants had zero AVC and MVC, while 6% (n = 211) and 4% (n = 156) had low, and 6% (n = 209) and 4% (n = 155) had high values of AVC and MVC, respectively. The AVC was independently associated with AD after adjusting for age, gender, and ethnicity ( P = .035). No association was noted between AVC groups and AD after adjustment for all covariates or MVC groups and AD in any model.

Analysis of biogenic carbonyl compounds in rainwater by stir bar sorptive extraction technique with chemical derivatization and gas chromatography‐mass spectrometry

PubMed Central

Lewis, Alastair C.; Shaw, Marvin D.

2016-01-01

Stir bar sorptive extraction is a powerful technique for the extraction and analysis of organic compounds in aqueous matrices. Carbonyl compounds are ubiquitous components in rainwater, however, it is a major challenge to accurately identify and sensitively quantify carbonyls from rainwater due to the complex matrix. A stir bar sorptive extraction technique was developed to efficiently extract carbonyls from aqueous samples following chemical derivatization by O‐(2,3,4,5,6‐pentafluorobenzyl) hydroxylamine hydrochloride. Several commercial stir bars in two sizes were used to simultaneously measure 29 carbonyls in aqueous samples with detection by gas chromatography with mass spectrometry. A 100 mL aqueous sample was extracted by stir bars and the analytes on stir bars were desorbed into a 2 mL solvent solution in an ultrasonic bath. The preconcentration Coefficient for different carbonyls varied between 30 and 45 times. The limits of detection of stir bar sorptive extraction with gas chromatography mass spectrometry for carbonyls (10–30 ng/L) were improved by ten times compared with other methods such as gas chromatography with electron capture detection and stir bar sorptive extraction with high‐performance liquid chromatography and mass spectrometry. The technique was used to determine carbonyls in rainwater samples collected in York, UK, and 20 carbonyl species were quantified including glyoxal, methylglyoxal, isobutenal, 2‐hydroxy ethanal. PMID:27928898

Effect of DA-9701 on Colorectal Distension-Induced Visceral Hypersensitivity in a Rat Model

PubMed Central

Kim, Eun Ran; Min, Byung-Hoon; Lee, Tae Ho; Son, Miwon; Rhee, Poong-Lyul

2014-01-01

Background/Aims DA-9701 is a newly developed drug made from the vegetal extracts of Pharbitidis semen and Co-rydalis tuber. The aim of this study was to evaluate the effect of DA-9701 on colorectal distension (CRD)-induced visceral hypersensitivity in a rat model. Methods Male Sprague-Dawley rats were subjected to neonatal colon irritation (CI) using CRD at 1 week after birth (CI group). At 6 weeks after birth, CRD was applied to these rats with a pressure of 20 to 90 mm Hg, and changes in the mean arterial pressure (MAP) were measured at baseline (i.e., without any drug administration) and after the administration of different doses of DA-9701. Results In the absence of DA-9701, the MAP changes after CRD were significantly higher in the CI group than in the control group at all applied pressures. In the control group, MAP changes after CRD were not significantly affected by the administration of DA-9701. In the CI group, however, the administration of DA-9701 resulted in a significant decrease in MAP changes after CRD. The administration of DA-9701 at a dose of 1.0 mg/kg produced a more significant decrease in MAP changes than the 0.3 mg/kg dose. Conclusions The administration of DA-9701 resulted in a significant increase in pain threshold in rats with CRD-induced visceral hypersensitivity. PMID:25071903

Effect of DA-9701 on colorectal distension-induced visceral hypersensitivity in a rat model.

PubMed

Kim, Eun Ran; Min, Byung-Hoon; Lee, Tae Ho; Son, Miwon; Rhee, Poong-Lyul

2014-07-01

DA-9701 is a newly developed drug made from the vegetal extracts of Pharbitidis semen and Co-rydalis tuber. The aim of this study was to evaluate the effect of DA-9701 on colorectal distension (CRD)-induced visceral hypersensitivity in a rat model. Male Sprague-Dawley rats were subjected to neonatal colon irritation (CI) using CRD at 1 week after birth (CI group). At 6 weeks after birth, CRD was applied to these rats with a pressure of 20 to 90 mm Hg, and changes in the mean arterial pressure (MAP) were measured at baseline (i.e., without any drug administration) and after the administration of different doses of DA-9701. In the absence of DA-9701, the MAP changes after CRD were significantly higher in the CI group than in the control group at all applied pressures. In the control group, MAP changes after CRD were not significantly affected by the administration of DA-9701. In the CI group, however, the administration of DA-9701 resulted in a significant decrease in MAP changes after CRD. The administration of DA-9701 at a dose of 1.0 mg/kg produced a more significant decrease in MAP changes than the 0.3 mg/kg dose. The administration of DA-9701 resulted in a significant increase in pain threshold in rats with CRD-induced visceral hypersensitivity.

Remote Leak Detection: Indirect Thermal Technique

NASA Technical Reports Server (NTRS)

Clements, Sandra

2002-01-01

Remote sensing technologies are being considered for efficient, low cost gas leak detection. Eleven specific techniques have been identified for further study and evaluation of several of these is underway. The Indirect Thermal Technique is one of the techniques that is being explored. For this technique, an infrared camera is used to detect the temperature change of a pipe or fitting at the site of a gas leak. This temperature change is caused by the change in temperature of the gas expanding from the leak site. During the 10-week NFFP program, the theory behind the technique was further developed, experiments were performed to determine the conditions for which the technique might be viable, and a proof-of-concept system was developed and tested in the laboratory.

Gastric Electrical Stimulation Decreases Gastric Distension-Induced Central Nociception Response through Direct Action on Primary Afferents

PubMed Central

Ouelaa, Wassila; Ghouzali, Ibtissem; Langlois, Ludovic; Fetissov, Serguei; Déchelotte, Pierre; Ducrotté, Philippe; Leroi, Anne Marie; Gourcerol, Guillaume

2012-01-01

Background & Aims Gastric electrical stimulation (GES) is an effective therapy to treat patients with chronic dyspepsia refractory to medical management. However, its mechanisms of action remain poorly understood. Methods Gastric pain was induced by performing gastric distension (GD) in anesthetized rats. Pain response was monitored by measuring the pseudo-affective reflex (e.g., blood pressure variation), while neuronal activation was determined using c-fos immunochemistry in the central nervous system. Involvement of primary afferents was assessed by measuring phosphorylation of ERK1/2 in dorsal root ganglia. Results GES decreased blood pressure variation induced by GD, and prevented GD-induced neuronal activation in the dorsal horn of the spinal cord (T9–T10), the nucleus of the solitary tract and in CRF neurons of the hypothalamic paraventricular nucleus. This effect remained unaltered within the spinal cord when sectioning the medulla at the T5 level. Furthermore, GES prevented GD-induced phosphorylation of ERK1/2 in dorsal root ganglia. Conclusions GES decreases GD-induced pain and/or discomfort likely through a direct modulation of gastric spinal afferents reducing central processing of visceral nociception. PMID:23284611

New alnico magnets fabricated from pre-alloyed gas-atomized powder through diverse consolidation techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, W.; Zhou, L.; Kassen, A. G.

2015-05-25

Fine Alnico 8 spherical powder produced by gas atomization was consolidated through hot pressing (HP), hot isostatic pressing (HIP), and compression molding and subsequent sintering (CMS) techniques. The effects of different fabrication techniques and processing parameters on microstructure and magnetic properties were analyzed and compared. The HP, HIP, and CMS magnets exhibited different features in microstructures and magnetic properties. Magnetically annealed at 840°C for 10 min and subsequently tempered at 650°C for 5h and 580°C for 15h, the HIP sample achieved the best coercivity (H cj =1845 Oe) due to spinodally decomposed (SD) phases with uniform and well-faceted mosaic morphology.more » As a result, the CMS sample had a lower Hcj than HIP and HP samples, but a higher remanence and thus the best energy product (6.5 MGOe) due to preferential grain alignment induced by abnormal grain growth.« less

Analytical techniques: A compilation

NASA Technical Reports Server (NTRS)

1975-01-01

A compilation, containing articles on a number of analytical techniques for quality control engineers and laboratory workers, is presented. Data cover techniques for testing electronic, mechanical, and optical systems, nondestructive testing techniques, and gas analysis techniques.

Study of the solid state of carbamazepine after processing with gas anti-solvent technique.

PubMed

Moneghini, M; Kikic, I; Voinovich, D; Perissutti, B; Alessi, P; Cortesi, A; Princivalle, F; Solinas, D

2003-09-01

The purpose of this study was to investigate the influence of supercritical CO2 processing on the physico-chemical properties of carbamazepine, a poorly soluble drug. The gas anti-solvent (GAS) technique was used to precipitate the drug from three different solvents (acetone, ethylacetate and dichloromethane) to study how they would affect the final product. The samples were analysed before and after treatment by scanning electron microscopy analysis and laser granulometry for possible changes in the habitus of the crystals. In addition, the solid state of the samples was studied by means of X-ray powder diffraction, differential scanning calorimetry, diffuse reflectance Fourier-transform infrared spectroscopy and hot stage microscopy. Finally, the in vitro dissolution tests were carried out. The solid state analysis of both samples untreated and treated with CO2, showed that the applied method caused a transition from the starting form III to the form I as well as determined a dramatic change of crystal morphology, resulting in needle-shaped crystals, regardless of the chosen solvent. In order to identify which process was responsible for the above results, carbamazepine was further precipitated from the same three solvents by traditional evaporation method (RV-samples). On the basis of this cross-testing, the solvents were found to be responsible for the reorganisation into a different polymorphic form, and the potential of the GAS process to produce micronic needle shaped particles, with an enhanced dissolution rate compared to the RV-carbamazepine, was ascertained.

[Research on diagnosis of gas-liquid detonation exhaust based on double optical path absortion spectroscopy technique].

PubMed

Lü, Xiao-Jing; Li, Ning; Weng, Chun-Sheng

2014-03-01

The effect detection of detonation exhaust can provide measurement data for exploring the formation mechanism of detonation, the promotion of detonation efficiency and the reduction of fuel waste. Based on tunable diode laser absorption spectroscopy technique combined with double optical path cross-correlation algorithm, the article raises the diagnosis method to realize the on-line testing of detonation exhaust velocity, temperature and H2O gas concentration. The double optical path testing system is designed and set up for the valveless pulse detonation engine with the diameter of 80 mm. By scanning H2O absorption lines of 1343nm with a high frequency of 50 kHz, the on-line detection of gas-liquid pulse detonation exhaust is realized. The results show that the optical testing system based on tunable diode laser absorption spectroscopy technique can capture the detailed characteristics of pulse detonation exhaust in the transient process of detonation. The duration of single detonation is 85 ms under laboratory conditions, among which supersonic injection time is 5.7 ms and subsonic injection time is 19.3 ms. The valveless pulse detonation engine used can work under frequency of 11 Hz. The velocity of detonation overflowing the detonation tube is 1,172 m x s(-1), the maximum temperature of detonation exhaust near the nozzle is 2 412 K. There is a transitory platform in the velocity curve as well as the temperature curve. H2O gas concentration changes between 0-7% during detonation under experimental conditions. The research can provide measurement data for the detonation process diagnosis and analysis, which is of significance to advance the detonation mechanism research and promote the research of pulse detonation engine control technology.

Safer Liquid Natural Gas

NASA Technical Reports Server (NTRS)

1976-01-01

After the disaster of Staten Island in 1973 where 40 people were killed repairing a liquid natural gas storage tank, the New York Fire Commissioner requested NASA's help in drawing up a comprehensive plan to cover the design, construction, and operation of liquid natural gas facilities. Two programs are underway. The first transfers comprehensive risk management techniques and procedures which take the form of an instruction document that includes determining liquid-gas risks through engineering analysis and tests, controlling these risks by setting up redundant fail safe techniques, and establishing criteria calling for decisions that eliminate or accept certain risks. The second program prepares a liquid gas safety manual (the first of its kind).

A Technique for Murine Irradiation in a Controlled Gas Environment

PubMed Central

Walb, M. C.; Moore, J. E.; Attia, A.; Wheeler, K. T.; Miller, M. S.; Munley, M. T.

2013-01-01

NASA’s extra-vehicular activities (EVAs) involve exposure to high energy photons while breathing 100% oxygen. Using previously verified mouse models, our laboratory is studying whether low dose irradiation under these hyperoxic conditions could lead to an increase in carcinogenic potential. To simulate the environment astronauts encounter during an EVA, enclosed chambers were constructed that allowed for mouse movement, controlled gas conditions, and uniform radiation dose delivery. Custom-built gas chambers with input/output gas valves and dividers that allowed for uniform gas flow were used to keep 6 unanesthetized mice separated while they were irradiated. The chambers were supplied with 100% oxygen or air using ball valves linked together with T-splitters. A calibrated ion chamber was used to verify the radiation dose distribution across an entire chamber. Mice were placed in the gas environments for 0.5 h, irradiated with a 10 or 18 MV photon beam from a medical linear accelerator, and left in their gas environment for 2 h post-irradiation. We irradiated 200 mice (5 different doses between 0–1000 mGy) under normoxic or 100% oxygen conditions. For the next step of this research, these mice will be euthanized 9 months post-irradiation, and lung tumors will be counted and sized to determine if hyperoxia increases the carcinogenic effect for this model. PMID:22846321

Gas flow headspace liquid phase microextraction.

PubMed

Yang, Cui; Qiu, Jinxue; Ren, Chunyan; Piao, Xiangfan; Li, Xifeng; Wu, Xue; Li, Donghao

2009-11-06

There is a trend towards the use of enrichment techniques such as microextraction in the analysis of trace chemicals. Based on the theory of ideal gases, theory of gas chromatography and the original headspace liquid phase microextraction (HS-LPME) technique, a simple gas flow headspace liquid phase microextraction (GF-HS-LPME) technique has been developed, where the extracting gas phase volume is increased using a gas flow. The system is an open system, where an inert gas containing the target compounds flows continuously through a special gas outlet channel (D=1.8mm), and the target compounds are trapped on a solvent microdrop (2.4 microL) hanging on the microsyringe tip, as a result, a high enrichment factor is obtained. The parameters affecting the enrichment factor, such as the gas flow rate, the position of the microdrop, the diameter of the gas outlet channel, the temperatures of the extracting solvent and of the sample, and the extraction time, were systematically optimized for four types of polycyclic aromatic hydrocarbons. The results were compared with results obtained from HS-LPME. Under the optimized conditions (where the extraction time and the volume of the extracting sample vial were fixed at 20min and 10mL, respectively), detection limits (S/N=3) were approximately a factor of 4 lower than those for the original HS-LPME technique. The method was validated by comparison of the GF-HS-LPME and HS-LPME techniques using data for PAHs from environmental sediment samples.

A new technique for pumping hydrogen gas

USGS Publications Warehouse

Friedman, I.; Hardcastle, K.

1970-01-01

A system for pumping hydrogen gas without isotopic fractionation has been developed. The pump contains uranium metal, which when heated to about 80??C reacts with hydrogen to form UH3. The UH3 is heated to above 500??C to decompose the hydride and regenerate the hydrogen. ?? 1970.

Sounding rocket thermal analysis techniques applied to GAS payloads. [Get Away Special payloads (STS)

NASA Technical Reports Server (NTRS)

Wing, L. D.

1979-01-01

Simplified analytical techniques of sounding rocket programs are suggested as a means of bringing the cost of thermal analysis of the Get Away Special (GAS) payloads within acceptable bounds. Particular attention is given to two methods adapted from sounding rocket technology - a method in which the container and payload are assumed to be divided in half vertically by a thermal plane of symmetry, and a method which considers the container and its payload to be an analogous one-dimensional unit having the real or correct container top surface area for radiative heat transfer and a fictitious mass and geometry which model the average thermal effects.

Effects of sensor location and the atmospheric stability on the accuracy of an inverse-dispersion technique for lagoon gas emission measurements

USDA-ARS?s Scientific Manuscript database

Measuring gas emission rates from wastewater lagoons and storage ponds using currently available micrometeorological techniques can be an arduous task because typical lagoon environments contain a variety of obstructions (e.g., berm, trees, buildings) to wind flow. These non-homogeneous terrain cond...

Computed tomography assessment of intestinal gas volumes in functional gastrointestinal disorders.

PubMed

Mc Williams, Sebastian R; Mc Laughlin, Patrick D; O'Connor, Owen J; Desmond, Alan N; Ní Laoíre, Aine; Shanahan, Fergus; Quigley, Eamonn Mm; Maher, Michael M

2012-10-01

Many patients with functional gastrointestinal disorders (FGIDs) rank sensations of bloating and distension among their most debilitating symptoms. Previous studies that have examined intestinal gas volume (IGV) in patients with FGIDs have employed a variety of invasive and imaging techniques. These studies are limited by small numbers and have shown conflicting results. The aim of our study was to estimate, using CT of the abdomen and pelvis (CTAP), IGV in patients attending FGID clinic and to compare IGV in patients with and without FGID. All CTAP (n = 312) performed on patients (n = 207) attending a specialized FGID clinic over 10-year period were included in this study. Patients were classified into one of 3 groups according to the established clinical grading system, as organic gastrointestinal disorder (OGID, ie, patients with an organic non-functional disorder, n = 84), FGID (n = 36) or organic and functional gastrointestinal disorder (OFGID, ie, patients with an organic and a functional disorder, n = 87). Two independent readers blinded to the diagnostic group calculated IGV using threshold based 3D region growing with OsiriX. Median IGVs for the FGID, OGID, and OFGID groups were 197.6, 220.6 and 155.0 mL, respectively. Stepwise linear regression revealed age at study, gender, and calculated body mass index to predict the log IGV with an r(2) of 0.116, and P < 0.001. There was a significant positive correlation between age and IGV in OGID (Spearman's = 0.253, P = 0.02) but this correlation was non-significant in the other groups. Although bloating is a classic symptom in FGID patients, IGV may not be increased compared with OGID and OFGID patients.

Manufacturing the Gas Diffusion Layer for PEM Fuel Cell Using a Novel 3D Printing Technique and Critical Assessment of the Challenges Encountered.

PubMed

Jayakumar, Arunkumar; Singamneni, Sarat; Ramos, Maximiano; Al-Jumaily, Ahmed M; Pethaiah, Sethu Sundar

2017-07-14

The conventional gas diffusion layer (GDL) of polymer electrolyte membrane (PEM) fuel cells incorporates a carbon-based substrate, which suffers from electrochemical oxidation as well as mechanical degradation, resulting in reduced durability and performance. In addition, it involves a complex manufacturing process to produce it. The proposed technique aims to resolve both these issues by an advanced 3D printing technique, namely selective laser sintering (SLS). In the proposed work, polyamide (PA) is used as the base powder and titanium metal powder is added at an optimised level to enhance the electrical conductivity, thermal, and mechanical properties. The application of selective laser sintering to fabricate a robust gas diffusion substrate for PEM fuel cell applications is quite novel and is attempted here for the first time.

Ethanol gas sensor based upon ZnO nanoparticles prepared by different techniques

NASA Astrophysics Data System (ADS)

Bhatia, Sonik; Verma, Neha; Bedi, R. K.

Nowadays, applications of nanosized materials have been an important issue in basic and applied sciences. In this investigation, Zinc Oxide (ZnO) nanoparticles were prepared by two different techniques (simple heat treatment, thermal evaporation-two zone furnaces). In order to control shape and size - ZnO nanoparticles prepared from heat treatment were used as a source for thermal evaporation method by using two zone split furnace by varying zone temperature (Zone 1-800 °C and Zone 2-400 °C). For both techniques 0.17 M of Zn acetate dihydrate is used as main precursor and film is deposited on glass substrate. Synthesized ZnO were characterized for XRD, FESEM, FTIR and UV-Vis spectrophotometer and LCR meter. XRD revealed hexagonal wurtzite structure with preferential orientation along (1 0 1) plane. FESEM observed that grain size in the range of range of ∼50 ± 5 nm. FTIR spectra showed that the peaks between 400 and 500 cm-1 for ZnO stretching modes. Optical properties has been studied and found that the observed band gap lies in the range of 3.32-3.36 eV. The higher value of capacitance is observed at lower frequency. Gas sensing properties showed the higher response in case of thermal evaporation as compared to simple heat treatment at an operating temperature of 250 °C.

Technique for measuring gas conversion factors

NASA Technical Reports Server (NTRS)

Singh, J. J.; Sprinkle, D. R. (Inventor)

1985-01-01

A method for determining hydrocarbon conversion factors for a flowmeter. A mixture of air, O2 and C sub x H sub y is burned and the partial paressure of O2 in the resulting gas is forced to equal the partial pressure of O2 in air. The flowrate of O2 flowing into the mixture is measured by flowmeter and the flowrate of C sub x H sub y flowing into the mixture is measured by the flowmeter conversion factor is to be determined. These measured values are used to calculate the conversion factor.

Effects of smoking on arterial distensibility, central aortic pressures and left ventricular mass.

PubMed

Markus, Marcello Ricardo Paulista; Stritzke, Jan; Baumeister, Sebastian Edgar; Siewert, Ulrike; Baulmann, Johannes; Hannemann, Anke; Schipf, Sabine; Meisinger, Christa; Dörr, Marcus; Felix, Stephan Burkhart; Keil, Ulrich; Völzke, Henry; Hense, Hans-Werner; Schunkert, Heribert

2013-10-03

The effects of smoking on central aortic pressures and the age-related increase in left ventricular mass (LVM) are largely unknown. We studied the relationship between smoking, arterial distensibility, central aortic pressures and left ventricular mass in two population-based studies. Data was obtained from two German population-based studies (KORA and SHIP, participants' ages 25-84 years). We identified 114 normotensive current smokers and 185 normotensive all-time non-smokers in KORA as well as 400 and 588 such individuals in SHIP. Echocardiographic LVM was obtained at baseline (T0) and follow-up after ten years (T1) in KORA and at follow-up (T1) in SHIP. Additionally, pulse-wave analysis-based central aortic pressure and augmentation index (AIx) were measured at T1 in KORA. Cross-sectional analysis, using KORA T0 and SHIP T1, revealed in both studies a higher covariate-adjusted LVM and left ventricular mass index (LVMI) in smokers as compared with non-smokers. Moreover, in the KORA T1 examination, the smokers demonstrated a more pronounced increase, relative to baseline, of LVM (+13.5%) and LVMI (+13.4%) compared to non-smokers (+8.59% and +8.65%; p=0.036 and 0.042, respectively). Additionally, at KORA T1 smokers had a higher central systolic blood pressure and higher AIx than non-smokers (p=0.012 and p=0.001, respectively). The difference in central aortic pressure due to enhanced and more prolonged wave reflection may explain our finding of a further pronounced increase in left ventricular wall thickness and mass over time in smokers. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Risk management technique for liquefied natural gas facilities

NASA Technical Reports Server (NTRS)

Fedor, O. H.; Parsons, W. N.

1975-01-01

Checklists have been compiled for planning, design, construction, startup and debugging, and operation of liquefied natural gas facilities. Lists include references to pertinent safety regulations. Methods described are applicable to handling of other hazardous materials.

Gas chromatography in space

NASA Technical Reports Server (NTRS)

Akapo, S. O.; Dimandja, J. M.; Kojiro, D. R.; Valentin, J. R.; Carle, G. C.

1999-01-01

Gas chromatography has proven to be a very useful analytical technique for in situ analysis of extraterrestrial environments as demonstrated by its successful operation on spacecraft missions to Mars and Venus. The technique is also one of the six scientific instruments aboard the Huygens probe to explore Titan's atmosphere and surface. A review of gas chromatography in previous space missions and some recent developments in the current environment of fiscal constraints and payload size limitations are presented.

Manufacturing the Gas Diffusion Layer for PEM Fuel Cell Using a Novel 3D Printing Technique and Critical Assessment of the Challenges Encountered

PubMed Central

Singamneni, Sarat; Ramos, Maximiano; Al-Jumaily, Ahmed M

2017-01-01

The conventional gas diffusion layer (GDL) of polymer electrolyte membrane (PEM) fuel cells incorporates a carbon-based substrate, which suffers from electrochemical oxidation as well as mechanical degradation, resulting in reduced durability and performance. In addition, it involves a complex manufacturing process to produce it. The proposed technique aims to resolve both these issues by an advanced 3D printing technique, namely selective laser sintering (SLS). In the proposed work, polyamide (PA) is used as the base powder and titanium metal powder is added at an optimised level to enhance the electrical conductivity, thermal, and mechanical properties. The application of selective laser sintering to fabricate a robust gas diffusion substrate for PEM fuel cell applications is quite novel and is attempted here for the first time. PMID:28773156

Pulsed-field-gradient measurements of time-dependent gas diffusion

NASA Technical Reports Server (NTRS)

Mair, R. W.; Cory, D. G.; Peled, S.; Tseng, C. H.; Patz, S.; Walsworth, R. L.

1998-01-01

Pulsed-field-gradient NMR techniques are demonstrated for measurements of time-dependent gas diffusion. The standard PGSE technique and variants, applied to a free gas mixture of thermally polarized xenon and O2, are found to provide a reproducible measure of the xenon diffusion coefficient (5.71 x 10(-6) m2 s-1 for 1 atm of pure xenon), in excellent agreement with previous, non-NMR measurements. The utility of pulsed-field-gradient NMR techniques is demonstrated by the first measurement of time-dependent (i.e., restricted) gas diffusion inside a porous medium (a random pack of glass beads), with results that agree well with theory. Two modified NMR pulse sequences derived from the PGSE technique (named the Pulsed Gradient Echo, or PGE, and the Pulsed Gradient Multiple Spin Echo, or PGMSE) are also applied to measurements of time dependent diffusion of laser polarized xenon gas, with results in good agreement with previous measurements on thermally polarized gas. The PGMSE technique is found to be superior to the PGE method, and to standard PGSE techniques and variants, for efficiently measuring laser polarized noble gas diffusion over a wide range of diffusion times. Copyright 1998 Academic Press.

Wellsite, laboratory, and mathematical techniques for determining sorbed gas content of coals and gas shales utilizing well cuttings

USGS Publications Warehouse

Newell, K.D.

2007-01-01

Drill cuttings can be used for desorption analyses but with more uncertainty than desorption analyses done with cores. Drill cuttings are not recommended to take the place of core, but in some circumstances, desorption work with cuttings can provide a timely and economic supplement to that of cores. The mixed lithologic nature of drill cuttings is primarily the source of uncertainty in their analysis for gas content, for it is unclear how to apportion the gas generated from both the coal and the dark-colored shale that is mixed in usually with the coal. In the Western Interior Basin Coal Basin in eastern Kansas (Pennsylvanian-age coals), dark-colored shales with normal (??? 100 API units) gamma-ray levels seem to give off minimal amounts of gas on the order of less than five standard cubic feet per ton (scf/ton). In some cuttings analyses this rule of thumb for gas content of the shale is adequate for inferring the gas content of coals, but shales with high-gamma-ray values (>150 API units) may yield several times this amount of gas. The uncertainty in desorption analysis of drill cuttings can be depicted graphically on a diagram identified as a "lithologic component sensitivity analysis diagram." Comparison of cuttings desorption results from nearby wells on this diagram, can sometimes yield an unique solution for the gas content of both a dark shale and coal mixed in a cuttings sample. A mathematical solution, based on equating the dry, ash-free gas-contents of the admixed coal and dark-colored shale, also yields results that are correlative to data from nearby cores. ?? 2007 International Association for Mathematical Geology.

Use of ionic liquids as stationary phases in hyphenated gas chromatography techniques.

PubMed

Ragonese, Carla; Sciarrone, Danilo; Tranchida, Peter Quinto; Dugo, Paola; Mondello, Luigi

2012-09-14

In the past decades a consistent number of ionic liquids have been specifically synthesized and evaluated as stationary phase in gas chromatography. Ionic liquid, also defined as "molten salts", are a class of organic non-molecular solvents liquid at room temperature (RTILs) that satisfy most of the requirements of a GC stationary phase, among which a high viscosity, the possibility to tune the selectivity (by changing the cation-anion combination) and a high thermal stability. The choice of the proper stationary phase plays a key role in the improvement/optimization of a GC method, and although the use of IL as stationary phases is still not well-established, the general interest in their applications has greatly increased, thanks to their particular properties. The present contribution provides an overview on recent evaluations and applications of IL stationary phases, focusing in particular on the use of these novel tools in hyphenated GC-based techniques. Copyright © 2012 Elsevier B.V. All rights reserved.

Time reversal technique for gas leakage detection.

PubMed

Maksimov, A O; Polovinka, Yu A

2015-04-01

The acoustic remote sensing of subsea gas leakage traditionally uses sonars as active acoustic sensors and hydrophones picking up the sound generated by a leak as passive sensors. When gas leaks occur underwater, bubbles are produced and emit sound at frequencies intimately related to their sizes. The experimental implementation of an acoustic time-reversal mirror (TRM) is now well established in underwater acoustics. In the basic TRM experiment, a probe source emits a pulse that is received on an array of sensors, time reversed, and re-emitted. After time reversal, the resulting field focuses back at the probe position. In this study, a method for enhancing operation of the passive receiving system has been proposed by using it in the regime of TRM. Two factors, the local character of the acoustic emission signal caused by the leakage and a resonant nature of the bubble radiation at their birth, make particularly effective scattering with the conjugate wave (CW). Analytical calculations are performed for the scattering of CW wave on a single bubble when CW is formed by bubble birthing wail received on an array, time reversed, and re-emitted. The quality of leakage detection depends on the spatio-temporal distribution of ambient noise.

Elimination of CT-detected gas bubbles derived from decompression illness with abdominal symptoms after a short hyperbaric oxygen treatment in a monoplace chamber: a case report.

PubMed

Oyaizu, Takuya; Enomoto, Mitsuhiro; Tsujimoto, Toshihide; Kojima, Yasushi; Okawa, Atsushi; Yagishita, Kazuyoshi

2017-01-01

We report the case of a 54-year-old male compressed-air worker with gas bubbles detected by computed tomography (CT). He had complained of strong abdominal pain 30 minutes after decompression after working at a pressure equivalent to 17 meters of sea water for three hours. The initial CT images revealed gas bubbles in the intrahepatic portal vein, pulmonary artery and bilateral femoral vein. After the first hyperbaric oxygen treatment (HBO₂ at 2.5 atmospheres absolute/ATA for 150 minutes), no bubbles were detected on repeat CT examination. The patient still exhibited abdominal distension, mild hypesthesia and slight muscle weakness in the upper extremities. Two sessions of U.S. Navy Treatment Table 6 (TT6) were performed on Days 6 and 7 after onset. The patient recovered completely on Day 7. This report describes the important role of CT imaging in evaluating intravascular gas bubbles as well as eliminating the diagnosis of other conditions when divers or compressed-air workers experience uncommon symptoms of decompression illness. In addition, a short treatment table of HBO₂ using non-TT6 HBO₂ treatment may be useful to reduce gas bubbles and the severity of decompression illness in emergent cases. Copyright© Undersea and Hyperbaric Medical Society.

Face expressive lifting (FEL): an original surgical concept combined with bipolar radiofrequency.

PubMed

Divaris, Marc; Blugerman, Guillermo; Paul, Malcolm D

2014-01-01

Aging can lead to changes in facial expressions, transforming the positive youth expression of happiness to negative expressions as sadness, tiredness, and disgust. Local skin distension is another consequence of aging, which can be difficult to treat with rejuvenation procedures. The "face expressive lifting" (FEL) is an original concept in facial rejuvenation surgery. On the one hand, FEL integrates established convergent surgical techniques aiming to correct the age-related negative facial expressions. On the other hand, FEL incorporates novel bipolar RF technology aiming to correct local skin distension. One hundred twenty-six patients underwent FEL procedure. Facial expression and local skin distension were assessed with 2 years follow-up. There was a correction of negative facial expression for 96 patients (76 %) and a tightening of local skin distension in 100 % of cases. FEL is an effective procedure taking into account and able to correct both age-related negative changes in facial expression and local skin distension using radiofrequency. Level of Evidence: Level IV, therapeutic study.

Determination of a cutoff value for pelvic floor distensibility using the Epi-no balloon to predict perineal integrity in vaginal delivery: ROC curve analysis. Prospective observational single cohort study.

PubMed

Zanetti, Miriam Raquel Diniz; Petricelli, Carla Dellabarba; Alexandre, Sandra Maria; Paschoal, Aline; Araujo Júnior, Edward; Nakamura, Mary Uchiyama

2016-04-01

Several risk factors are involved in perineal lacerations during vaginal delivery. However, little is known about the influence of perineal distensibility as a protective factor. The aim here was to determine a cutoff value for pelvic floor distensibility measured using the Epi-no balloon, which could be used as a predictive factor for perineal integrity in vaginal delivery. Prospective observational single cohort study conducted in a maternity hospital. A convenience sample of 227 consecutive at-term parturients was used. All women had a single fetus in the vertex presentation, with up to 9.0 cm of dilation. The maximum dilation of the Epi-no balloon was measured using a tape measure after it had been inflated inside the vagina up to the parturients' maximum tolerance. The receiver operating characteristic (ROC) curve was used to obtain the Epi-no circumference measurement with best sensitivity and specificity. Among the 161 patients who were included in the study, 50.9% underwent episiotomy, 21.8% presented lacerations and 27.3% retained an intact perineum. Age > 25.9 years; number of pregnancies > 3.4; number of deliveries > 2.2 and circumference measured by Epi-no > 21.4 cm were all directly correlated with an intact perineum. Circumference measurements using the Epi-no balloon that were greater than 20.8 cm showed sensitivity and specificity of 70.5% and 66.7% (area under curve = 0.713), respectively, as a predictive factor for an intact perineum in vaginal delivery. Circumferences greater than 20.8 cm achieved using the Epi-no balloon are a predictive factor for perineal integrity in parturients.

CHARACTERIZATION OF UPPER THORACIC SPINAL NEURONS RESPONDING TO ESOPHAGEAL DISTENSION IN DIABETIC RATS

PubMed Central

Qin, Chao; Ghorbani, Marie L. M.; Wu, Mingyuan; Farber, Jay P.; Ma, Jianxin; Foreman, Robert D.

2009-01-01

The aim of this study was to examine spinal neuronal processing of innocuous and noxious mechanical inputs from the esophagus in diabetic rats. Streptozotocin (50 mg/kg, ip) was used to induce diabetes in 15 male Sprague-Dawley rats, and vehicle (10 mM citrate buffer) was injected into 15 rats as control. Four to eleven weeks after injections, extracellular potentials of single thoracic (T3) spinal neurons were recorded in pentobarbital anesthetized, paralyzed, and ventilated rats. Esophageal distensions (ED, 0.2, 0.4 ml, 20s) were produced by water inflation of a latex balloon in the thoracic esophagus. Noxious ED (0.4 ml, 20 s) altered activity of 44% (55/126) and 38% (50/132) of spinal neurons in diabetic and control rats, respectively. The short-lasting excitatory responses to ED were encountered more frequently in diabetic rats (27/42 vs 15/41, P<0.05). Spinal neurons with low threshold for excitatory responses to ED were more frequently encountered in diabetic rats (33/42 vs 23/41, P<0.05). However, mean excitatory responses and duration of responses to noxious ED were significantly reduced for high-threshold neurons in diabetic rats (7.4±1.1 vs 13.9±3.3 imp/s; 19.0±2.3 vs 31.2±5.5 s; P<0.05). In addition, more large size somatic receptive fields were found for spinal neurons with esophageal input in diabetic rats than in control rats (28/42 vs 19/45, P<0.05). These results suggested that diabetes influenced response characteristics of thoracic spinal neurons receiving mechanical esophageal input, which might indicate an altered spinal visceroceptive processing underlying diabetic esophageal neuropathy. PMID:19027368

Gas Fride Heat Pumps : The Present and Future

NASA Astrophysics Data System (ADS)

Kurosawa, Shigekichi; Ogura, Masao

In japan techniques for saving energy is an important goal since energy resources such as oil and nuclear power are limited. Recently gas fired absorption heat pumps and gas engine driven heat pumps have been installed in facilifies such as hotels, swimming pools and offices.
In this article recent techniques, applications and future aspects for gas fired heat pumps are explained.

Current Techniques of Growing Algae Using Flue Gas from Exhaust Gas Industry: a Review.

PubMed

Huang, Guanhua; Chen, Feng; Kuang, Yali; He, Huan; Qin, An

2016-03-01

The soaring increase of flue gas emission had caused global warming, environmental pollution as well as climate change. Widespread concern on reduction of flue gas released from industrial plants had considered the microalgae as excellent biological materials for recycling the carbon dioxide directly emitted from exhaust industries. Microalgae also have the potential to be the valuable feedback for renewable energy production due to their high growth rate and abilities to sequester inorganic carbon through photosynthetic process. In this review article, we will illustrate important relative mechanisms in the metabolic processes of biofixation by microalgae and their recent experimental researches and advances of sequestration of carbon dioxide by microalgae on actual industrial and stimulate flue gases, novel photobioreactor cultivation systems as well as the perspectives and limitations of microalgal cultivation in further development.

Barostat testing of rectal sensation and compliance in humans: comparison of results across two centres and overall reproducibility.

PubMed

Cremonini, F; Houghton, L A; Camilleri, M; Ferber, I; Fell, C; Cox, V; Castillo, E J; Alpers, D H; Dewit, O E; Gray, E; Lea, R; Zinsmeister, A R; Whorwell, P J

2005-12-01

We assessed reproducibility of measurements of rectal compliance and sensation in health in studies conducted at two centres. We estimated samples size necessary to show clinically meaningful changes in future studies. We performed rectal barostat tests three times (day 1, day 1 after 4 h and 14-17 days later) in 34 healthy participants. We measured compliance and pressure thresholds for first sensation, urgency, discomfort and pain using ascending method of limits and symptom ratings for gas, urgency, discomfort and pain during four phasic distensions (12, 24, 36 and 48 mmHg) in random order. Results obtained at the two centres differed minimally. Reproducibility of sensory end points varies with type of sensation, pressure level and method of distension. Pressure threshold for pain and sensory ratings for non-painful sensations at 36 and 48 mmHg distension were most reproducible in the two centres. Sample size calculations suggested that crossover design is preferable in therapeutic trials: for each dose of medication tested, a sample of 21 should be sufficient to demonstrate 30% changes in all sensory thresholds and almost all sensory ratings. We conclude that reproducibility varies with sensation type, pressure level and distension method, but in a two-centre study, differences in observed results of sensation are minimal and pressure threshold for pain and sensory ratings at 36-48 mmHg of distension are reproducible.

Minor isotope safeguards techniques (MIST): Analysis and visualization of gas centrifuge enrichment plant process data using the MSTAR model

NASA Astrophysics Data System (ADS)

Shephard, Adam M.; Thomas, Benjamin R.; Coble, Jamie B.; Wood, Houston G.

2018-05-01

This paper presents a development related to the use of minor isotope safeguards techniques (MIST) and the MSTAR cascade model as it relates to the application of international nuclear safeguards at gas centrifuge enrichment plants (GCEPs). The product of this paper is a derivation of the universal and dimensionless MSTAR cascade model. The new model can be used to calculate the minor uranium isotope concentrations in GCEP product and tails streams or to analyze, visualize, and interpret GCEP process data as part of MIST. Applications of the new model include the detection of undeclared feed and withdrawal streams at GCEPs when used in conjunction with UF6 sampling and/or other isotopic measurement techniques.

Chemical composition and the nutritive value of pistachio epicarp (in situ degradation and in vitro gas production techniques).

PubMed

Bakhshizadeh, Somayeh; Taghizadeh, Akbar; Janmohammadi, Hossein; Alijani, Sadegh

2014-01-01

The nutritive value of pistachio epicarp (PE) was evaluated by in situ and in vitro techniques. Chemical analysis indicated that PE was high in crude protein (11.30%) and low in neutral detergent fiber (26.20%). Total phenols, total tannins, condensed tannins and hydrolysable tannins contents in PE were 8.29%, 4.48%, 0.49% and 3.79%, respectively. Ruminal dry matter and crude protein degradation after 48 hr incubation were 75.21% and 82.52%, respectively. The gas production volume at 48 hr for PE was 122.47 mL g(-1)DM. As a whole, adding polyethylene glycol (PEG) to PE increased (p < 0.05) gas production volumes, organic matter digestibility and the metabolizable energy that illustrated inhibitory effect of phenolics on rumen microbial fermentation and the positive influence of PEG on digestion PE. The results showed that PE possessed potentials to being used as feed supplements.

Electron temperature and density measurement of tungsten inert gas arcs with Ar-He shielding gas mixture

NASA Astrophysics Data System (ADS)

Kühn-Kauffeldt, M.; Marques, J.-L.; Forster, G.; Schein, J.

2013-10-01

The diagnostics of atmospheric welding plasma is a well-established technology. In most cases the measurements are limited to processes using pure shielding gas. However in many applications shielding gas is a mixture of various components including metal vapor in gas metal arc welding (GMAW). Shielding gas mixtures are intentionally used for tungsten inert gas (TIG) welding in order to improve the welding performance. For example adding Helium to Argon shielding gas allows the weld geometry and porosity to be influenced. Yet thermal plasmas produced with gas mixtures or metal vapor still require further experimental investigation. In this work coherent Thomson scattering is used to measure electron temperature and density in these plasmas, since this technique allows independent measurements of electron and ion temperature. Here thermal plasmas generated by a TIG process with 50% Argon and 50% Helium shielding gas mixture have been investigated. Electron temperature and density measured by coherent Thomson scattering have been compared to the results of spectroscopic measurements of the plasma density using Stark broadening of the 696.5 nm Argon spectral line. Further investigations of MIG processes using Thomson scattering technique are planned.

DSMC simulation of rarefied gas flows under cooling conditions using a new iterative wall heat flux specifying technique

NASA Astrophysics Data System (ADS)

Akhlaghi, H.; Roohi, E.; Myong, R. S.

2012-11-01

Micro/nano geometries with specified wall heat flux are widely encountered in electronic cooling and micro-/nano-fluidic sensors. We introduce a new technique to impose the desired (positive/negative) wall heat flux boundary condition in the DSMC simulations. This technique is based on an iterative progress on the wall temperature magnitude. It is found that the proposed iterative technique has a good numerical performance and could implement both positive and negative values of wall heat flux rates accurately. Using present technique, rarefied gas flow through micro-/nanochannels under specified wall heat flux conditions is simulated and unique behaviors are observed in case of channels with cooling walls. For example, contrary to the heating process, it is observed that cooling of micro/nanochannel walls would result in small variations in the density field. Upstream thermal creep effects in the cooling process decrease the velocity slip despite of the Knudsen number increase along the channel. Similarly, cooling process decreases the curvature of the pressure distribution below the linear incompressible distribution. Our results indicate that flow cooling increases the mass flow rate through the channel, and vice versa.

Argentine gas system underway for Gas del Estado

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bosch, H.

Gas del Estado's giant 1074-mile Centro-Oeste pipeline project - designed to ultimately transport over 350 million CF/day of natural gas from the Neuquen basin to the Campo Duran-Buenos Aires pipeline system - is now underway. The COGASCO consortium of Dutch and Argentine companies awarded the construction project will also operate and maintain the system for 15 years after its completion. In addition to the 30-in. pipelines, the agreement calls for a major compressor station at the gas field, three intermediate compressor stations, a gas-treatment plant, liquids-recovery facilities, and the metering, control, communications, and maintenance equipment for the system. Fabricated inmore » Holland, the internally and externally coated pipe will be double-jointed to 80-ft lengths after shipment to Argentina; welders will use conventional manual-arc techniques to weld the pipeline in the field.« less

Pantothenic Acid

MedlinePlus

... distension) due to reduced intestinal function, and for gas following surgery or pregnancy. A nasal spray containing dexpanthenol is used to reduce the feeling of having a stuffed nose (nasal obstruction) and to reduce a runny nose (nasal discharge).

Non-invasive assessment of carotid PWV via accelerometric sensors: validation of a new device and comparison with established techniques.

PubMed

Di Lascio, Nicole; Bruno, Rosa Maria; Stea, Francesco; Bianchini, Elisabetta; Gemignani, Vincenzo; Ghiadoni, Lorenzo; Faita, Francesco

2014-01-01

Carotid pulse wave velocity (PWV) is considered as a surrogate marker for carotid stiffness and its assessment is increasingly being used in clinical practice. However, at the moment, its estimation needs specific equipment and a moderate level of technical expertise; moreover, it is based on a mathematical model. The aim of this study was to validate a new system for non-invasive and model-free carotid PWV assessment based on accelerometric sensors by comparison with currently used techniques. Accelerometric PWV (accPWV) values were obtained in 97 volunteers free of cardiovascular disease (age 24-85 years) and compared with standard ultrasound-based carotid stiffness parameters, such as carotid PWV (cPWV), relative distension (relD) and distensibility coefficient (DC). Moreover, the comparison between accPWV measurements and carotid-femoral PWV (cfPWV) was performed. Accelerometric PWV evaluations showed a significant correlation with cPWV measurements (R = 0.67), relD values (R = 0.66) and DC assessments (R = 0.64). These values were also significantly correlated with cfPWV evaluations (R = 0.46). In addition, the first attempt success rate was equal to 76.8 %. The accelerometric system allows a simple and quick local carotid stiffness evaluation and the values obtained with this system are significantly correlated with known carotid stiffness biomarkers. Therefore, the presented device could provide a concrete opportunity for an easy carotid stiffness evaluation even in clinical practice.

Assessing the Rayleigh Intensity Remote Leak Detection Technique

NASA Technical Reports Server (NTRS)

Clements, Sandra

2001-01-01

Remote sensing technologies are being considered for efficient, low cost gas leak detection. An exploratory project to identify and evaluate remote sensing technologies for application to gas leak detection is underway. During Phase 1 of the project, completed last year, eleven specific techniques were identified for further study. One of these, the Rayleigh Intensity technique, would make use of changes in the light scattered off of gas molecules to detect and locate a leak. During the 10-week Summer Faculty Fellowship Program, the scatter of light off of gas molecules was investigated. The influence of light scattered off of aerosols suspended in the atmosphere was also examined to determine if this would adversely affect leak detection. Results of this study indicate that in unconditioned air, it will be difficult, though perhaps not impossible, to distinguish between a gas leak and natural variations in the aerosol content of the air. Because information about the particle size distribution in clean room environments is incomplete, the applicability in clean rooms is uncertain though more promising than in unconditioned environments. It is suggested that problems caused by aerosols may be overcome by using the Rayleigh Intensity technique in combination with another remote sensing technique, the Rayleigh Doppler technique.

Mars Atmospheric Capture and Gas Separation

NASA Technical Reports Server (NTRS)

Muscatello, Anthony; Santiago-Maldonado, Edgardo; Gibson, Tracy; Devor, Robert; Captain, James

2011-01-01

The Mars atmospheric capture and gas separation project is selecting, developing, and demonstrating techniques to capture and purify Martian atmospheric gases for their utilization for the production of hydrocarbons, oxygen, and water in ISRU systems. Trace gases will be required to be separated from Martian atmospheric gases to provide pure C02 to processing elements. In addition, other Martian gases, such as nitrogen and argon, occur in concentrations high enough to be useful as buffer gas and should be captured as welL To achieve these goals, highly efficient gas separation processes will be required. These gas separation techniques are also required across various areas within the ISRU project to support various consumable production processes. The development of innovative gas separation techniques will evaluate the current state-of-the-art for the gas separation required, with the objective to demonstrate and develop light-weight, low-power methods for gas separation. Gas separation requirements include, but are not limited to the selective separation of: (1) methane and water from un-reacted carbon oxides (C02- CO) and hydrogen typical of a Sabatier-type process, (2) carbon oxides and water from unreacted hydrogen from a Reverse Water-Gas Shift process, (3) carbon oxides from oxygen from a trash/waste processing reaction, and (4) helium from hydrogen or oxygen from a propellant scavenging process. Potential technologies for the separations include freezers, selective membranes, selective solvents, polymeric sorbents, zeolites, and new technologies. This paper and presentation will summarize the results of an extensive literature review and laboratory evaluations of candidate technologies for the capture and separation of C02 and other relevant gases.

Increasing plasma free fatty acids in healthy subjects induces aortic distensibility changes seen in obesity.

PubMed

Rider, Oliver J; Holloway, Cameron J; Emmanuel, Yaso; Bloch, Edward; Clarke, Kieran; Neubauer, Stefan

2012-05-01

Elevated free fatty acid (FFA) levels are known to impair aortic elastic function. In obesity, FFA levels are elevated and aortic distensibility (AD) reduced in a pattern that predominantly affects the distal aorta. Despite this, the role of FFAs in obesity-related aortic stiffness remains unclear. Using vascular MRI, we aimed to determine if (1) FFA level correlated with AD in obesity; and (2) whether elevating FFA acutely and subacutely in normal-weight subjects reproduced the distal pattern of AD change in obesity. To do this, regional AD was recorded in 35 normal-weight and 70 obese subjects and then correlated with FFA levels. When compared with normal weight, obesity was associated with reduced AD in a pattern predominantly affecting the distal aorta (ascending aorta by -22%, proximal descending aorta by -25%, and abdominal aorta by -35%; P<0.001). After controlling for age, blood pressure, and body mass index, FFA levels remained negatively correlated with abdominal AD (r=-0.43, P<0.01). In 2 further normal-weight groups, AD was recorded before and after elevation of FFA levels with intralipid infusion (by +535%, n=9) and a 5-day high-fat, low-carbohydrate diet (by +48%, n=14). Both intralipid infusion and a low-carbohydrate diet resulted in reduced abdominal AD (infusion -22%, diet -28%; both P<0.05), reproducing the distal pattern AD reduction seen in obesity. These findings suggest that elevated FFA impair AD in obesity and provide a potential therapeutic target to improve aortic elastic function in obesity.

Medical Problems in High Mountain Environments. A Handbook for Medical Officers

DTIC Science & Technology

1994-02-01

include abdominal pain, nausea, abdominal distension , intestinal gas and frequent diarrhea. Acutely, symptoms may also include weakness, loss of...altitude terrain. As might be expected, the greatest effects are on aerobic activity while anaerobic exercise and muscular strength are virtually

Development of a New Fundamental Measuring Technique for the Accurate Measurement of Gas Flowrates by Means of Laser Doppler Anemometry

NASA Astrophysics Data System (ADS)

Dopheide, D.; Taux, G.; Krey, E.-A.

1990-01-01

In the Physikalisch-Technische Bundesanstalt (PTB), a research test facility for the accurate measurement of gas (volume and mass) flowrates has been set up in the last few years on the basis of a laser Doppler anemometer (LDA) with a view to directly measuring gas flowrates with a relative uncertainty of only 0,1%. To achieve this, it was necessary to develop laser Doppler anemometry into a precision measuring technique and to carry out detailed investigations on stationary low-turbulence nozzle flow. The process-computer controlled test facility covers the flowrate range from 100 to 4000 m3/h (~0,03 - 1,0 m3/s), any flowrate being measured directly, immediately and without staggered arrangement of several flow meters. After the development was completed, several turbine-type gas meters were calibrated and international comparisons carried out. The article surveys the most significant aspects of the work and provides an outlook on future developments with regard to the miniaturization of optical flow and flowrate sensors for industrial applications.

Component greenhouse gas fluxes and radiative balance from two deltaic marshes in Louisiana: Pairing chamber techniques and eddy covariance

USGS Publications Warehouse

Krauss, Ken W.; Holm, Guerry O.; Perez, Brian C.; McWhorter, David E.; Cormier, Nicole; Moss, Rebecca; Johnson, Darren; Neubauer, Scott C; Raynie, Richard C

2016-01-01

Coastal marshes take up atmospheric CO2 while emitting CO2, CH4, and N2O. This ability to sequester carbon (C) is much greater for wetlands on a per-area basis than from most ecosystems, facilitating scientific, political, and economic interest in their value as greenhouse gas sinks. However, the greenhouse gas balance of Gulf of Mexico wetlands is particularly understudied. We describe the net ecosystem exchange (NEEc) of CO2 and CH4 using eddy covariance (EC) in comparison with fluxes of CO2, CH4, and N2O using chambers from brackish and freshwater marshes in Louisiana, USA. From EC, we found that 182 g C m-2 y-1 was lost through NEEc from the brackish marsh. Of this, 11 g C m-2 y-1 resulted from net CH4 emissions and the remaining 171 g C m-2 y-1 resulted from net CO2 emissions. In contrast, -290 g C m2 y-1 was taken up through NEEc by the freshwater marsh, with 47 g C m-2 y-1 emitted as CH4 and -337 g C m-2 y-1 taken up as CO2. From chambers, we discovered that neither site had large fluxes of N2O. Sustained-flux greenhouse gas accounting metrics indicated that both marshes had a positive (warming) radiative balance, with the brackish marsh having a substantially greater warming effect than the freshwater marsh. That net respiratory emissions of CO2 and CH4 as estimated through chamber techniques were 2-4 times different from emissions estimated through EC requires additional understanding of the artifacts created by different spatial and temporal sampling footprints between techniques.

Gas-phase spectroscopy of synephrine by laser desorption supersonic jet technique.

PubMed

Ishiuchi, Shun-ichi; Asakawa, Toshiro; Mitsuda, Haruhiko; Miyazaki, Mitsuhiko; Chakraborty, Shamik; Fujii, Masaaki

2011-09-22

In our previous work, we found that synephrine has six conformers in the gas phase, while adrenaline, which is a catecholamine and has the same side chain as synephrine, has been reported to have only two conformers. To determine the conformational geometries of synephrine, we measured resonance enhanced multiphoton ionization, ultraviolet-ultraviolet hole burning, and infrared dip spectra by utilizing the laser desorption supersonic jet technique. By comparing the observed infrared spectra with theoretical ones, we assigned geometries except for the orientations of the phenolic OH group. Comparison between the determined structures of synephrine and those of 2-methylaminno-1-phenylethanol, which has the same side chain as synephrine but no phenol OH group, leads to the conclusion that the phenolic OH group in synephrine does not affect the conformational flexibility of the side chain. In the case of adrenaline, which is expected to have 12 conformers if there are no interactions between the catecholic OH groups and the side chain, some interactions possibly exist between them because only two conformations are observed. By estimation of the dipole-dipole interaction energy between partial dipole moments of the catecholic OH groups and the side chain, it was concluded that the dipole-dipole interaction stabilizes specific conformers which are actually observed. © 2011 American Chemical Society

Loss of visceral pain following colorectal distension in an endothelin-3 deficient mouse model of Hirschsprung's disease

PubMed Central

Zagorodnyuk, Vladimir P; Kyloh, Melinda; Nicholas, Sarah; Peiris, Heshan; Brookes, Simon J; Chen, Bao Nan; Spencer, Nick J

2011-01-01

Abstract Endothelin peptides and their endogenous receptors play a major role in nociception in a variety of different organs. They also play an essential role in the development of the enteric nervous system. Mice with deletions of the endothelin-3 gene (lethal spotted mice, ls/ls) develop congenital aganglionosis. However, little is known about how nociception might be affected in the aganglionic rectum of mice deficient in endothelin-3. In this study we investigated changes in spinal afferent innervation and visceral pain transmission from the aganglionic rectum in ls/ls mice. Electromyogram recordings from anaesthetized ls/ls mice revealed a deficit in visceromotor responses arising from the aganglionic colorectum in response to noxious colorectal distension. Loss of visceromotor responses (VMRs) in ls/ls mice was selective, as no reduction in VMRs was detected after stimulation of the bladder or somatic organs. Calcitonin gene related peptide (CGRP) immunoreactivity, retrograde neuronal tracing and extracellular afferent recordings from the aganglionic rectum revealed decreased colorectal spinal innervation, combined with a reduction in mechanosensitivity of rectal afferents. The sensory defect in ls/ls mice is primarily associated with changes in low threshold wide dynamic range rectal afferents. In conclusion, disruption of endothelin 3 gene expression not only affects development and function of the enteric nervous system, but also specific classes of spinal rectal mechanoreceptors, which are required for visceral nociception from the colorectum. PMID:21320883

[A review of mixed gas detection system based on infrared spectroscopic technique].

PubMed

Dang, Jing-Min; Fu, Li; Yan, Zi-Hui; Zheng, Chuan-Tao; Chang, Yu-Chun; Chen, Chen; Wang, Yi-Din

2014-10-01

In order to provide the experiences and references to the researchers who are working on infrared (IR) mixed gas detection field. The proposed manuscript reviews two sections of the aforementioned field, including optical multiplexing structure and detection method. At present, the coherent light sources whose representative are quantum cascade laser (QCL) and inter-band cascade laser(ICL) become the mainstream light source in IR mixed gas detection, which replace the traditional non-coherent light source, such as IR radiation source and IR light emitting diode. In addition, the photon detector which has a super high detectivity and very short response time is gradually beyond thermal infrared detector, dominant in the field of infrared detector. The optical multiplexing structure is the key factor of IR mixed gas detection system, which consists of single light source multi-plexing detection structure and multi light source multiplexing detection structure. Particularly, single light source multiplexing detection structure is advantages of small volume and high integration, which make it a plausible candidate for the portable mixed gas detection system; Meanwhile, multi light source multiplexing detection structure is embodiment of time division multiplex, frequency division multiplexing and wavelength division multiplexing, and become the leading structure of the mixed gas detection system because of its wider spectral range, higher spectral resolution, etc. The detection method applied to IR mixed gas detection includes non-dispersive infrared (NDIR) spectroscopy, wavelength and frequency-modulation spectroscopy, cavity-enhanced spectroscopy and photoacoustic spectroscopy, etc. The IR mixed gas detection system designed by researchers after recognizing the whole sections of the proposed system, which play a significant role in industrial and agricultural production, environmental monitoring, and life science, etc.

A technique for administering xenon gas anesthesia during surgical procedures in mice.

PubMed

Ruder, Arne Mathias; Schmidt, Michaela; Ludiro, Alessia; Riva, Marco A; Gass, Peter

2014-11-01

Carrying out invasive procedures in animals requires the administration of anesthesia. Xenon gas offers advantages as an anesthetic agent compared with other agents, such as its protection of the brain and heart from hypoxia-induced damage. The high cost of xenon gas has limited its use as an anesthetic in animal experiments, however. The authors designed and constructed simple boxes for the induction and maintenance of xenon gas and isoflurane anesthesia in small rodents in order to minimize the amount of xenon gas that is wasted. While using their anesthesia delivery system to anesthetize pregnant mice undergoing caesarean sections, they measured the respiratory rates of the anesthetized mice, the survival of the pups and the percentages of oxygen and carbon dioxide within the system to confirm the system's safety.

PIGC™ - A low cost fugitive emissions and methane detection system using advanced gas filter correlation techniques for local and wide area monitoring

NASA Astrophysics Data System (ADS)

Lachance, R. L.; Gordley, L. L.; Marshall, B. T.; Fisher, J.; Paxton, G.; Gubeli, J. F.

2015-12-01

Currently there is no efficient and affordable way to monitor gas releases over small to large areas. We have demonstrated the ability to accurately measure key greenhouse and pollutant gasses with low cost solar observations using the breakthrough sensor technology called the "Pupil Imaging Gas Correlation", PIGC™, which provides size and complexity reduction while providing exceptional resolution and coverage for various gas sensing applications. It is a practical implementation of the well-known Gas Filter Correlation Radiometry (GFCR) technique used for the HALOE and MOPITT satellite instruments that were flown on successful NASA missions in the early 2000s. This strong space heritage brings performance and reliability to the ground instrument design. A methane (CH4) abundance sensitivity of 0.5% or better of ambient column with uncooled microbolometers has been demonstrated with 1 second direct solar observations. These under $10 k sensors can be deployed in precisely balanced autonomous grids to monitor the flow of chosen gasses, and infer their source locations. Measureable gases include CH4, 13CO2, N2O, NO, NH3, CO, H2S, HCN, HCl, HF, HDO and others. A single instrument operates in a dual operation mode, at no additional cost, for continuous (real-time 24/7) local area perimeter monitoring for the detection of leaks for safety & security needs, looking at an artificial light source (for example a simple 60 W light bulb placed 100 m away), while simultaneously allowing solar observation for quasi-continuous wide area total atmospheric column scanning (3-D) for environmental monitoring (fixed and mobile configurations). The second mode of operation continuously quantifies the concentration and flux of specific gases over different ground locations, determined the amount of targeted gas being released from the area or getting into the area from outside locations, allowing better tracking of plumes and identification of sources. This paper reviews the

Fabrication of nanowire channels with unidirectional alignment and controlled length by a simple, gas-blowing-assisted, selective-transfer-printing technique.

PubMed

Kim, Yong-Kwan; Kang, Pil Soo; Kim, Dae-Il; Shin, Gunchul; Kim, Gyu Tae; Ha, Jeong Sook

2009-03-01

A printing-based lithographic technique for the patterning of V(2)O(5) nanowire channels with unidirectional orientation and controlled length is introduced. The simple, directional blowing of a patterned polymer stamp with N(2) gas, inked with randomly distributed V(2)O(5) nanowires, induces alignment of the nanowires perpendicular to the long axis of the line patterns. Subsequent stamping on the amine-terminated surface results in the selective transfer of the aligned nanowires with a controlled length corresponding to the width of the relief region of the polymer stamp. By employing such a gas-blowing-assisted, selective-transfer-printing technique, two kinds of device structures consisting of nanowire channels and two metal electrodes with top contact, whereby the nanowires were aligned either parallel (parallel device) or perpendicular (serial device) to the current flow in the conduction channel, are fabricated. The electrical properties demonstrate a noticeable difference between the two devices, with a large hysteresis in the parallel device but none in the serial device. Systematic analysis of the hysteresis and the electrical stability account for the observed hysteresis in terms of the proton diffusion in the water layer of the V(2)O(5) nanowires, induced by the application of an external bias voltage higher than a certain threshold voltage.

Isotopic and Geochemical Investigation of Two Distinct Mars Analog Environments Using Evolved Gas Techniques in Svalbard, Norway

NASA Technical Reports Server (NTRS)

Stern, Jennifer Claire; Mcadam, Amy Catherine; Ten Kate, Inge L.; Bish, David L.; Blake, David F.; Morris, Richard V.; Bowden, Roxane; Fogel, Marilyn L.; Glamoclija, Mihaela; Mahaffy, Paul R.;

Calf tissue liquid stowage and muscular and deep vein distension in orthostatic tests after a 90-day head down bed rest

NASA Astrophysics Data System (ADS)

Arbeille, P.A.; Kerbeci, P.; Audebert, P.; Capri, A.; Pascaud, L.

2005-08-01

The objectives were to assess the contribution of (1) the calf veins distension and(2) the tissue liquid stowage during standtest, to orthostatic intolerance "OI" after a head down bed rest (HDBR) of 90days. Method: The population consisted of a control group (Co-gr, n=9) and an exercise Fly wheel counter-measure group (CM-gr, n=9). Calf vein cross sectional area (CSA) and surrounding tissue liquid content (tissue image darkness) were assessed by echography during pre and post HDBR stand-tests. Results: From supine to standing (post HDBR), the Tibial and muscular vein CSA increased significantly in non tolerant subjects whereas in tolerant subjects the vein CSA did not change. Post HDBR the tissue image darkness (proportional to tissue liquid content) increased more from supine to standing in non tolerant than in tolerant subjects. No significant difference were found between Co and exercise CM groups. Conclusion: High calf vein CSA and tissue liquid content increase at post-HDBR stand-test were significantly correlated with occurrence of OI but not with CM.

Acute effects of oral melatonin administration on arterial distensibility, as determined by carotid-femoral pulse wave velocity, in healthy young men

PubMed Central

Yildiz, Mustafa; Sahin, Banu; Sahin, Alparslan

2006-01-01

The aim of the present study was to investigate the effects of melatonin administration on arterial distensibility by using carotid-femoral (aortic) pulse wave velocity (PWV) measurements in healthy young men. Ten men were studied (five men in the melatonin group and five men in the placebo group) by physicians. Carotid-femoral (aortic) PWV, blood pressure and plasma melatonin were measured in the supine position before and 60 min after oral administration of melatonin or placebo. Although carotid-femoral (aortic) PWV, systolic blood pressure and mean blood pressure were decreased, pulse wave propagation time and plasma melatonin levels were increased at 60 min after oral melatonin (1 mg) administration (P=0.04, P=0.04, P=0.04, P=0.04 and P=0.04, respectively). No significant differences were found between all parameters in the placebo group (P>0.05). In conclusion, these findings indicate that melatonin administration, compared with placebo, decreased carotid-femoral PWV and systolic blood pressure in the supine position in healthy young men. Administration of melatonin may have an inhibitory effect on sympathetic tone. PMID:18651024

Molecular wake shield gas analyzer

NASA Technical Reports Server (NTRS)

Hoffman, J. H.

1980-01-01

Techniques for measuring and characterizing the ultrahigh vacuum in the wake of an orbiting spacecraft are studied. A high sensitivity mass spectrometer that contains a double mass analyzer consisting of an open source miniature magnetic sector field neutral gas analyzer and an identical ion analyzer is proposed. These are configured to detect and identify gas and ion species of hydrogen, helium, nitrogen, oxygen, nitric oxide, and carbon dioxide and any other gas or ion species in the 1 to 46 amu mass range. This range covers the normal atmospheric constituents. The sensitivity of the instrument is sufficient to measure ambient gases and ion with a particle density of the order of one per cc. A chemical pump, or getter, is mounted near the entrance aperture of the neutral gas analyzer which integrates the absorption of ambient gases for a selectable period of time for subsequent release and analysis. The sensitivity is realizable for all but rare gases using this technique.

Cavity-enhanced resonant photoacoustic spectroscopy with optical feedback cw diode lasers: A novel technique for ultratrace gas analysis and high-resolution spectroscopy.

PubMed

Hippler, Michael; Mohr, Christian; Keen, Katherine A; McNaghten, Edward D

2010-07-28

Cavity-enhanced resonant photoacoustic spectroscopy with optical feedback cw diode lasers (OF-CERPAS) is introduced as a novel technique for ultratrace gas analysis and high-resolution spectroscopy. In the scheme, a single-mode cw diode laser (3 mW, 635 nm) is coupled into a high-finesse linear cavity and stabilized to the cavity by optical feedback. Inside the cavity, a build-up of laser power to at least 2.5 W occurs. Absorbing gas phase species inside the cavity are detected with high sensitivity by the photoacoustic effect using a microphone embedded in the cavity. To increase sensitivity further, coupling into the cavity is modulated at a frequency corresponding to a longitudinal resonance of an organ pipe acoustic resonator (f=1.35 kHz and Q approximately 10). The technique has been characterized by measuring very weak water overtone transitions near 635 nm. Normalized noise-equivalent absorption coefficients are determined as alpha approximately 4.4x10(-9) cm(-1) s(1/2) (1 s integration time) and 2.6x10(-11) cm(-1) s(1/2) W (1 s integration time and 1 W laser power). These sensitivities compare favorably with existing state-of-the-art techniques. As an advantage, OF-CERPAS is a "zero-background" method which increases selectivity and sensitivity, and its sensitivity scales with laser power.

New technique for the direct analysis of food powders confined in a small hole using transversely excited atmospheric CO(2) laser-induced gas plasma.

PubMed

Khumaeni, Ali; Ramli, Muliadi; Deguchi, Yoji; Lee, Yong Inn; Idris, Nasrullah; Kurniawan, Koo Hendrik; Lie, Tjung Jie; Kagawa, Kiichiro

2008-12-01

Taking advantage of the differences between the interactions of transversely excited atmospheric (TEA) CO(2) lasers with metal and with organic powder, a new technique for the direct analysis of food powder samples has been developed. In this technique, the powder samples were placed into a small hole with a diameter of 2 mm and a depth of 3 mm and covered by a metal mesh. The TEA CO(2) laser (1500 mJ, 200 ns) was focused on the powder sample surfaces, passing through the metal mesh, at atmospheric pressure in nitrogen gas. It is hypothesized that the small hole functions to confine the powder particles and suppresses the blowing-off of sample, while the metal mesh works as the source of electrons to initiate the strong gas breakdown plasma. The confined powder particles are then ablated by laser irradiation and the ablated particles move into the strong gas breakdown plasma region to be atomized and excited; this method cannot be applied for the case of Nd:YAG lasers because in such case the metal mesh itself was ablated by the laser irradiation. A quantitative analysis of a milk powder sample containing different concentrations of Ca was successfully demonstrated, resulting in a good linear calibration curve with high precision.

Gas transfer in a bubbly wake flow

NASA Astrophysics Data System (ADS)

Karn, A.; Gulliver, J. S.; Monson, G. M.; Ellis, C.; Arndt, R. E. A.; Hong, J.

2016-05-01

The present work reports simultaneous bubble size and gas transfer measurements in a bubbly wake flow of a hydrofoil, designed to be similar to a hydroturbine blade. Bubble size was measured by a shadow imaging technique and found to have a Sauter mean diameter of 0.9 mm for a reference case. A lower gas flow rate, greater liquid velocities, and a larger angle of attack all resulted in an increased number of small size bubbles and a reduced weighted mean bubble size. Bubble-water gas transfer is measured by the disturbed equilibrium technique. The gas transfer model of Azbel (1981) is utilized to characterize the liquid film coefficient for gas transfer, with one scaling coefficient to reflect the fact that characteristic turbulent velocity is replaced by cross-sectional mean velocity. The coefficient was found to stay constant at a particular hydrofoil configuration while it varied within a narrow range of 0.52-0.60 for different gas/water flow conditions.

Formation of Structured Water and Gas Hydrate by the Use of Xenon Gas in Vegetable Tissue

NASA Astrophysics Data System (ADS)

Ando, Hiroko; Suzuki, Toru; Kawagoe, Yoshinori; Makino, Yoshio; Oshita, Seiichi

Freezing is a valuable technique for food preservation. However, vegetables are known to be softening remarkably after freezing and thawing process. It is expected to find alternative technique instead of freezing. Recently, the application of structured water and/or gas hydrate had been attempted to prolong the preservation of vegetable. In this study, the formation process of structure water and/or gas hydrate in pure water and carrot tissue was investigated by using NMR relaxation times, T1 and T2, of which applying condition was up to 0.4MPa and 0.8MPa at 5oC. Under the pressure of 0.4MPa, no gas hydrate was appeared, however, at 0.8MPa, formation of gas hydrate was recognized in both water and carrot tissue. Once the gas hydrate formation process in carrot tissue started, T1 and T2 increased remarkably. After that, as the gas hydrate developed, then T1 and T2 turned to decrease. Since this phenomenon was not observed in pure water, it is suggested that behavior of NMR relaxation time just after the formation of gas hydrate in carrot tissue may be peculiar to compartment system such as inter and intracellular spaces.

Modified Technique For Chemisorption Measurements

NASA Technical Reports Server (NTRS)

Schryer, David R.; Brown, Kenneth G.; Schryer, Jacqueline

1989-01-01

In measurements of chemisorption of CO on Pt/SnO2 catalyst observed that if small numbers of relatively large volumes of adsorbate gas are passed through sample, very little removal of CO detected. In these cases little or no CO has been chemisorbed on Pt/SnO2. Technique of using large number of small volumes of adsorbate gas to measure chemisorption applicable to many gas/material combinations other than CO on Pt/SnO2. Volume used chosen so that at least 10 percent of adsorbate gas removed during each exposure.

The inhibitory effect of granisetron on ventrolateral medulla neuron responses to colorectal distension in rats.

PubMed

Panteleev, Sergey S; Martseva, Alexandra А; Lyubashina, Olga А

2015-02-15

Irritable bowel syndrome (IBS) is one of the most widespread functional gastrointestinal disorders characterized by abdominal pain. A key pathophysiological mechanism of abdominal pain is associated with disturbances of serotonergic transmission in feedback control loops of endogenous pain modulation in which the ventrolateral medulla (VLM) plays an important role. The receptors to serotonin (5-HT), and particularly the serotonin 3 (5-HT3) receptors have been extensively used as a potential target for abdominal pain treatment of IBS patients due to antinociceptive features of the 5-HT3 receptor antagonists. The precise mechanisms underlying the antinociceptive action of these antagonists remain unclear. The main objective of our study was to evaluate the involvement of the 5-HT3 receptors in abdominal pain transmission within the VLM. Experiments were carried out on urethane-anaesthetized rats using the animal model of abdominal pain. Noxious colorectal distension (CRD) with a pressure of 80mmHg induced a significant increase in VLM neuron-evoked activity and depressor reactions (171.1±12.7% and 64±1.8% to baseline, accordingly). Selective blockade of the 5-HT3 receptors with granisetron at doses of 1.0 or 2.0mg/kg (i.v) resulted in long-lasting (90min) dose-dependent inhibition of VLM neuron-evoked activity and depressor reactions. When brainstem dorsal surface applications of granisetron (10 or 20µM) were used, the changes were more pronounced. These results suggest involvement of the 5-HT3 receptors in abdominal pain transmission within the VLM, which will be discussed in relation to the central antinociceptive effect of granisetron. Copyright © 2015 Elsevier B.V. All rights reserved.

A smog chamber comparison of a microfluidic derivatization measurement of gas-phase glyoxal and methylglyoxal with other analytical techniques

NASA Astrophysics Data System (ADS)

Pang, X.; Lewis, A. C.; Richard, A.; Baeza-Romero, M. T.; Adams, T. J.; Ball, S. M.; Daniels, M. J. S.; Goodall, I. C. A.; Monks, P. S.; Peppe, S.; Ródenas García, M.; Sánchez, P.; Muñoz, A.

2013-06-01

A microfluidic lab-on-a-chip derivatization technique has been developed to measure part per billion volume (ppbV) mixing ratios of gaseous glyoxal (GLY) and methylglyoxal (MGLY), and the method compared with other techniques in a smog chamber experiment. The method uses o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) as a derivatization reagent and a microfabricated planar glass micro-reactor comprising an inlet, gas and fluid splitting and combining channels, mixing junctions, and a heated capillary reaction microchannel. The enhanced phase contact area-to-volume ratio and the high heat transfer rate in the micro-reactor result in a fast and highly efficient derivatization reaction, generating an effluent stream ready for direct introduction to a gas chromatograph-mass spectrometer (GC-MS). A linear response for GLY was observed over a calibration range 0.7 to 400 ppbV, and for MGLY of 1.2 to 300 ppbV, when derivatized under optimal reaction conditions. The method detection limits (MDLs) were 80 pptV and 200 pptV for GLY and MGLY respectively, calculated as 3 times the standard deviation of the S/N of the blank sample chromatograms. These MDLs are below or close to typical concentrations in clean ambient air. The feasibility of the technique was assessed by applying the methodology under controlled conditions to quantify of α-dicarbonyls formed during the photo-oxidation of isoprene in a large scale outdoor atmospheric simulation chamber (EUPHORE). Good general agreement was seen between microfluidic measurements and Fourier Transform Infra Red (FTIR), Broad Band Cavity Enhanced Absorption Spectroscopy (BBCEAS) and a detailed photochemical chamber box modelling calculation for both GLY and MGLY. Less good agreement was found with Proton-Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS) and Solid Phase Microextraction (SPME) derivatization methods for MGLY measurement.

Stark effect spectrophone for continuous absorption spectra monitoring. [a technique for gas analysis

NASA Technical Reports Server (NTRS)

Kavaya, M. J. (Inventor)

1981-01-01

A Stark effect spectrophone using a pulsed or continuous wave laser having a beam with one or more absorption lines of a constituent of an unknown gas is described. The laser beam is directed through windows of a closed cell while the unknown gas to be modified flows continuously through the cell between electric field plates disposed in the cell on opposite sides of the beam path through the cell. When the beam is pulsed, energy absorbed by the gas increases at each point along the beam path according to the spectral lines of the constituents of the gas for the particular field strengths at those points. The pressure measurement at each point during each pulse of energy yields a plot of absorption as a function of electric field for simultaneous detection of the gas constituents. Provision for signal averaging and modulation is included.

Application of dense gas techniques for the production of fine particles.

PubMed

Foster, Neil R; Dehghani, Fariba; Charoenchaitrakoo, Kiang M; Warwick, Barry

2003-01-01

The feasibility of using dense gas techniques such as rapid expansion of supercritical solutions (RESS) and aerosol solvent extraction system (ASES) for micronization of pharmaceutical compounds is demonstrated. The chiral nonsteroidal anti-inflammatory racemic ibuprofen is soluble in carbon dioxide at 35 degrees C and pressures above 90 bar. The particle size decreased to less than 2 microm while the degree of crystallinity was slightly decreased when processed by RESS. The dissolution rate of the ibuprofen (a poorly water-soluble compound) was significantly enhanced after processing by RESS. The nonsteroidal anti-inflammatory drug Cu2(indomethacin)4L2(Cu-Indo); (L = dimethylformamide [DMF]), which possessed very low solubility in supercritical CO2, was successfully micronized by ASES at 25 degrees C and 68.9 bar using DMF as the solvent and CO2 as the antisolvent. The concentration of solute dramatically influenced the precipitate characteristics. The particles obtained from the ASES process were changed from bipyramidal to spherical, with particle size less than 5 microm, as the concentration increased from 5 to 100 mg/g. A further increase in solute concentration to 200 mg/g resulted in large porous spheres, between 20 and 50 micron, when processing Cu-Indo by the ASES method. The dissolution rate of the micronized Cu-Indo was significantly higher than the commercial product.

A Dual-Line Detection Rayleigh Scattering Diagnostic Technique for the Combustion of Hydrocarbon Fuels and Filtered UV Rayleigh Scattering for Gas Velocity Measurements

NASA Technical Reports Server (NTRS)

Otugen, M. Volkan

1997-01-01

Non-intrusive techniques for the dynamic measurement of gas flow properties such as density, temperature and velocity, are needed in the research leading to the development of new generation high-speed aircraft. Accurate velocity, temperature and density data obtained in ground testing and in-flight measurements can help understand the flow physics leading to transition and turbulence in supersonic, high-altitude flight. Such non-intrusive measurement techniques can also be used to study combustion processes of hydrocarbon fuels in aircraft engines. Reliable, time and space resolved temperature measurements in various combustor configurations can lead to a better understanding of high temperature chemical reaction dynamics thus leading to improved modeling and better prediction of such flows. In view of this, a research program was initiated at Polytechnic University's Aerodynamics Laboratory with support from NASA Lewis Research Center through grants NAG3-1301 and NAG3-1690. The overall objective of this program has been to develop laser-based, non-contact, space- and time-resolved temperature and velocity measurement techniques. In the initial phase of the program a ND:YAG laser-based dual-line Rayleigh scattering technique was developed and tested for the accurate measurement of gas temperature in the presence of background laser glare. Effort was next directed towards the development of a filtered, spectrally-resolved Rayleigh/Mie scattering technique with the objective of developing an interferometric method for time-frozen velocity measurements in high-speed flows utilizing the uv line of an ND:YAG laser and an appropriate molecular absorption filter. This effort included both a search for an appropriate filter material for the 266 nm laser line and the development and testing of several image processing techniques for the fast processing of Fabry-Perot images for velocity and temperature information. Finally, work was also carried out for the development of

Application of capillary gas chromatography mass spectrometry/computer techniques to synoptic survey of organic material in bed sediment

USGS Publications Warehouse

Steinheimer, T.R.; Pereira, W.E.; Johnson, S.M.

1981-01-01

A bed sediment sample taken from an area impacted by heavy industrial activity was analyzed for organic compounds of environmental significance. Extraction was effected on a Soxhlet apparatus using a freeze-dried sample. The Soxhlet extract was fractionated by silica gel micro-column adsorption chromatography. Separation and identification of the organic compounds was accomplished by capillary gas chromatography/mass spectrometry techniques. More than 50 compounds were identified; these include saturated hydrocarbons, olefins, aromatic hydrocarbons, alkylated polycyclic aromatic hydrocarbons, and oxygenated compounds such as aldehydes and ketones. The role of bed sediments as a source or sink for organic pollutants is discussed. ?? 1981.

Quantification of OH and HO2 radicals during the low-temperature oxidation of hydrocarbons by Fluorescence Assay by Gas Expansion technique

PubMed Central

Blocquet, Marion; Schoemaecker, Coralie; Amedro, Damien; Herbinet, Olivier; Battin-Leclerc, Frédérique; Fittschen, Christa

2013-01-01

•OH and •HO2 radicals are known to be the key species in the development of ignition. A direct measurement of these radicals under low-temperature oxidation conditions (T = 550–1,000 K) has been achieved by coupling a technique named fluorescence assay by gas expansion, an experimental technique designed for the quantification of these radicals in the free atmosphere, to a jet-stirred reactor, an experimental device designed for the study of low-temperature combustion chemistry. Calibration allows conversion of relative fluorescence signals to absolute mole fractions. Such radical mole fraction profiles will serve as a benchmark for testing chemical models developed to improve the understanding of combustion processes. PMID:24277836

Determination of gas volume trapped in a closed fluid system

NASA Technical Reports Server (NTRS)

Hunter, W. F.; Jolley, J. E.

1971-01-01

Technique involves extracting known volume of fluid and measuring system before and after extraction, volume of entrapped gas is then computed. Formula derived from ideal gas laws is basis of this method. Technique is applicable to thermodynamic cycles and hydraulic systems.

Fe3O4/γ-Fe2O3 nanoparticle multilayers deposited by the Langmuir-Blodgett technique for gas sensors application.

PubMed

Capone, S; Manera, M G; Taurino, A; Siciliano, P; Rella, R; Luby, S; Benkovicova, M; Siffalovic, P; Majkova, E

2014-02-04

Fe3O4/γ-Fe2O3 nanoparticles (NPs) based thin films were used as active layers in solid state resistive chemical sensors. NPs were synthesized by high temperature solution phase reaction. Sensing NP monolayers (ML) were deposited by Langmuir-Blodgett (LB) techniques onto chemoresistive transduction platforms. The sensing ML were UV treated to remove NP insulating capping. Sensors surface was characterized by scanning electron microscopy (SEM). Systematic gas sensing tests in controlled atmosphere were carried out toward NO2, CO, and acetone at different concentrations and working temperatures of the sensing layers. The best sensing performance results were obtained for sensors with higher NPs coverage (10 ML), mainly for NO2 gas showing interesting selectivity toward nitrogen oxides. Electrical properties and conduction mechanisms are discussed.

Real-time detection of dielectric anisotropy or isotropy in unconventional oil-gas reservoir rocks supported by the oblique-incidence reflectivity difference technique

NASA Astrophysics Data System (ADS)

Zhan, Honglei; Wang, Jin; Zhao, Kun; Lű, Huibin; Jin, Kuijuan; He, Liping; Yang, Guozhen; Xiao, Lizhi

2016-12-01

Current geological extraction theory and techniques are very limited to adequately characterize the unconventional oil-gas reservoirs because of the considerable complexity of the geological structures. Optical measurement has the advantages of non-interference with the earth magnetic fields, and is often useful in detecting various physical properties. One key parameter that can be detected using optical methods is the dielectric permittivity, which reflects the mineral and organic properties. Here we reported an oblique-incidence reflectivity difference (OIRD) technique that is sensitive to the dielectric and surface properties and can be applied to characterization of reservoir rocks, such as shale and sandstone core samples extracted from subsurface. The layered distribution of the dielectric properties in shales and the uniform distribution in sandstones are clearly identified using the OIRD signals. In shales, the micro-cracks and particle orientation result in directional changes of the dielectric and surface properties, and thus, the isotropy and anisotropy of the rock can be characterized by OIRD. As the dielectric and surface properties are closely related to the hydrocarbon-bearing features in oil-gas reservoirs, we believe that the precise measurement carried with OIRD can help in improving the recovery efficiency in well-drilling process.

Time-Resolved Images of Laser-Induced Gas Ignition Using High-Speed Photographic and Spectroscopic Techniques

NASA Astrophysics Data System (ADS)

Chen, Ying-Ling; Lewis, J. W. L.; Parigger, C. G.

1997-11-01

Two-dimensional visualization of laser-induced spark ignition in atmospheric-pressure gases is reported. Laser-induced breakdown in air, O2 and combustible NH_3/O2 mixture was achieved using a 1064 nm, Nd:YAG laser of approximately 6 ns pulse width, focused at 10-mm above a 60-mm diameter flat-flame burner. An argon sheath-gas flow was used to stabilize the core flowfield. High-speed photographic techniques were applied to trace a complete sequence of kernel development of a single breakdown or ignition event. Thermochemical characteristics of the post-breakdown regime were analyzed by laser-induced fluorescence spectroscopy (LIFS). Spatial distribution of NH free radical observed by planar-LIF showed the contours of the developing flame-front. The corresponding NH temperature maps achieved by excitation LIFS and Boltzmann plot are also presented.

Gas-absorption process

DOEpatents

Stephenson, Michael J.; Eby, Robert S.

1978-01-01

This invention is an improved gas-absorption process for the recovery of a desired component from a feed-gas mixture containing the same. In the preferred form of the invention, the process operations are conducted in a closed-loop system including a gas-liquid contacting column having upper, intermediate, and lower contacting zones. A liquid absorbent for the desired component is circulated through the loop, being passed downwardly through the column, regenerated, withdrawn from a reboiler, and then recycled to the column. A novel technique is employed to concentrate the desired component in a narrow section of the intermediate zone. This technique comprises maintaining the temperature of the liquid-phase input to the intermediate zone at a sufficiently lower value than that of the gas-phase input to the zone to effect condensation of a major part of the absorbent-vapor upflow to the section. This establishes a steep temperature gradient in the section. The stripping factors below this section are selected to ensure that virtually all of the gases in the downflowing absorbent from the section are desorbed. The stripping factors above the section are selected to ensure re-dissolution of the desired component but not the less-soluble diluent gases. As a result, a peak concentration of the desired component is established in the section, and gas rich in that component can be withdrawn therefrom. The new process provides important advantages. The chief advantage is that the process operations can be conducted in a single column in which the contacting zones operate at essentially the same pressure.

Comparison of mass spectrometry-based electronic nose and solid phase microextraction gas chromatography-mass spectrometry technique to assess infant formula oxidation.

PubMed

Fenaille, François; Visani, Piero; Fumeaux, René; Milo, Christian; Guy, Philippe A

2003-04-23

Two headspace techniques based on mass spectrometry detection (MS), electronic nose, and solid phase microextraction coupled to gas chromatography-mass spectrometry (SPME-GC/MS) were evaluated for their ability to differentiate various infant formula powders based on changes of their volatiles upon storage. The electronic nose gave unresolved MS fingerprints of the samples gas phases that were further submitted to principal component analysis (PCA). Such direct MS recording combined to multivariate treatment enabled a rapid differentiation of the infant formulas over a 4 week storage test. Although MS-based electronic nose advantages are its easy-to-use aspect and its meaningful data interpretation obtained with a high throughput (100 samples per 24 h), its greatest disadvantage is that the present compounds could not be identified and quantified. For these reasons, a SPME-GC/MS measurement was also investigated. This technique allowed the identification of saturated aldehydes as the main volatiles present in the headspace of infant milk powders. An isotope dilution assay was further developed to quantitate hexanal as a potential indicator of infant milk powder oxidation. Thus, hexanal content was found to vary from roughly 500 and 3500 microg/kg for relatively non-oxidized and oxidized infant formulas, respectively.

Right Pulmonary Artery Distensibility Index (RPAD Index). A field study of an echocardiographic method to detect early development of pulmonary hypertension and its severity even in the absence of regurgitant jets for Doppler evaluation in heartworm-infected dogs.

PubMed

Venco, Luigi; Mihaylova, Liliya; Boon, June A

2014-11-15

Despite the term "heartworm disease" Dirofilaria immitis infection in dogs should be considered a pulmonary arterial disease that might only involve the right heart structures in its late stage. Chronic infection by adult heartworms in dogs results in proliferative endoarteritis leading to progressively increasing pulmonary artery pressure due to reduced elasticity. Elasticity allows the pulmonary arteries to stretch in response to each pulse and helps maintain a relatively constant pressure in the arteries despite the pulsating nature of the blood flow. Pulmonary artery distensibility for both acute and chronic pulmonary hypertension has been investigated in humans using MRI and has been correlated with the severity of hypertension and its outcome and treatment response. The aim of the present study was to investigate whether echocardiographic measurement of the percentage change in diameter of the right pulmonary artery in systole and diastole (distensibility) may be of value in assessing the presence and severity of pulmonary hypertension in heartworm-infected dogs. The Right Pulmonary Artery Distensibility Index (RPAD Index) (which is calculated as the difference in diameter of the right pulmonary artery in systole and diastole) was calculated in healthy and naturally infected heartworm-positive dogs. The right pulmonary artery was chosen because it is usually affected earlier and to a greater degree. Data were obtained from healthy heartworm-free dogs without any clinical, radiographic, or echocardiographic signs of pulmonary hypertension; naturally infected heartworm-positive dogs in different stages of the disease in which pulmonary pressure could be measured by Doppler echocardiography (using tricuspid and or pulmonary regurgitation velocity and pressure gradient); and naturally infected heartworm-positive dogs in different stages of the disease (with or without tricuspid and or pulmonary regurgitation) in which the pulmonary pressure was measured

Controls on the physical properties of gas-hydrate-bearing sediments because of the interaction between gas hydrate and porous media

USGS Publications Warehouse

Lee, Myung W.; Collett, Timothy S.

2005-01-01

Physical properties of gas-hydrate-bearing sediments depend on the pore-scale interaction between gas hydrate and porous media as well as the amount of gas hydrate present. Well log measurements such as proton nuclear magnetic resonance (NMR) relaxation and electromagnetic propagation tool (EPT) techniques depend primarily on the bulk volume of gas hydrate in the pore space irrespective of the pore-scale interaction. However, elastic velocities or permeability depend on how gas hydrate is distributed in the pore space as well as the amount of gas hydrate. Gas-hydrate saturations estimated from NMR and EPT measurements are free of adjustable parameters; thus, the estimations are unbiased estimates of gas hydrate if the measurement is accurate. However, the amount of gas hydrate estimated from elastic velocities or electrical resistivities depends on many adjustable parameters and models related to the interaction of gas hydrate and porous media, so these estimates are model dependent and biased. NMR, EPT, elastic-wave velocity, electrical resistivity, and permeability measurements acquired in the Mallik 5L-38 well in the Mackenzie Delta, Canada, show that all of the well log evaluation techniques considered provide comparable gas-hydrate saturations in clean (low shale content) sandstone intervals with high gas-hydrate saturations. However, in shaly intervals, estimates from log measurement depending on the pore-scale interaction between gas hydrate and host sediments are higher than those estimates from measurements depending on the bulk volume of gas hydrate.

Data acquisition techniques for exploiting the uniqueness of the time-of-flight mass spectrometer: Application to sampling pulsed gas systems

NASA Technical Reports Server (NTRS)

Lincoln, K. A.

1980-01-01

Mass spectra are produced in most mass spectrometers by sweeping some parameter within the instrument as the sampled gases flow into the ion source. It is evident that any fluctuation in the gas during the sweep (mass scan) of the instrument causes the output spectrum to be skewed in its mass peak intensities. The time of flight mass spectrometer (TOFMS) with its fast, repetitive mode of operation produces spectra without skewing or varying instrument parameters and because all ion species are ejected from the ion source simultaneously, the spectra are inherently not skewed despite rapidly changing gas pressure or composition in the source. Methods of exploiting this feature by utilizing fast digital data acquisition systems, such as transient recorders and signal averagers which are commercially available are described. Applications of this technique are presented including TOFMS sampling of vapors produced by both pulsed and continuous laser heating of materials.

Heterodyne method for high specificity gas detection.

NASA Technical Reports Server (NTRS)

Dimeff, J.; Donaldson, R. W.; Gunter, W. D., Jr.; Jaynes, D. N.; Margozzi, A. P.; Deboo, G. J.; Mcclatchie, E. A.; Williams, K. G.

1971-01-01

This paper describes a new technique for measuring trace quantities of gases. The technique involves the use of a reference cell (containing a known amount of the gas being sought) and a sample cell (containing an unknown amount of the same gas) wherein the gas densities are modulated. Light passing through the two cells in sequence is modulated in intensity at the vibrational-rotational lines characteristic of the absorption spectrum for the gas of interest. Since the absorption process is nonlinear, modulating the two absorption cells at two different frequencies gives rise to a heterodyning effect, which in turn introduces sum and difference frequencies in the detected signal. Measuring the ratio of the difference frequency signal for example, to the signal introduced by the reference cell provides a normalized measure of the amount of the gas in the sample cell. The readings produced are thereby independent of source intensity, window transparency, and detector sensitivity. Experimental evaluation of the technique suggests that it should be applicable to a wide range of gases, that it should be able to reject spurious signals due to unwanted gases, and that it should be sensitive to concentrations of the order of 10 to the minus 8th power when used with a sample cell of only 20 cm length.

A smog chamber comparison of a microfluidic derivatisation measurement of gas-phase glyoxal and methylglyoxal with other analytical techniques

NASA Astrophysics Data System (ADS)

Pang, xiaobing; Lewis, Alastair; Rickard, Andrew R.; Baeza-Romero, Maria Teresa; Adams, Thomas J.; Ball, Stephen M.; Goodall, Iain C. A.; Monks, Paul S.; Peppe, Salvatore; Ródenas García, Milagros; Sánchez, Pilar; Muñoz, Amalia

2014-05-01

A microfluidic lab-on-a-chip derivatisation technique has been developed to measure part per billion (ppbV) mixing ratios of gaseous glyoxal (GLY) and methylglyoxal (MGLY), and the method is compared with other techniques in a smog chamber experiment. The method uses o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) as a derivatisation reagent and a microfabricated planar glass micro-reactor comprising an inlet, gas and fluid splitting and combining channels, mixing junctions, and a heated capillary reaction microchannel. The enhanced phase contact area-to-volume ratio and the high heat transfer rate in the micro-reactor result in a fast and highly efficient derivatisation reaction, generating an effluent stream ready for direct introduction to a gas chromatograph-mass spectrometer (GC-MS). A linear response for GLY was observed over a calibration range 0.7 to 400 ppbV, and for MGLY of 1.2 to 300 ppbV, when derivatised under optimal reaction conditions. The analytical performance shows good accuracy (6.6 % for GLY and 7.5 % for MGLY), suitable precision (< 12.0 %) and method detection limits (MDLs) (75 pptV for GLY and 185 pptV for MGLY) with a time resolution of 30 minutes. These MDLs are below or close to typical concentrations of these compounds observed in ambient air. The microfluidic derivatisation technique would be appropriate for ambient α-dicarbonyl measurements in a range of field environments based on its performance in a large-scale outdoor atmospheric simulation chamber (EUPHORE). The feasibility of the technique was assessed by applying the methodology to quantify of α-dicarbonyls formed during the photo-oxidation of isoprene in the EUPHORE chamber. Good correlations were found between microfluidic measurements and Fourier Transform InfraRed spectroscopy (FTIR) with the correlation coefficient (r2) of 0.84, Broad Band Cavity Enhanced Absorption Spectroscopy (BBCEAS) (r2 = 0.75), solid phase micro extraction (SPME) (r2 = 0.89), and a

Measurement of gas viscosity using photonic crystal fiber

NASA Astrophysics Data System (ADS)

Gao, R.-K.; Sheehe, S. L.; Kurtz, J.; O'Byrne, S.

2016-11-01

A new measurement technique for gas viscosity coefficient is designed and demonstrated using the technique of tunable diode laser absorption spectroscopy (TDLAS). Gas flow is driven by a pressure gradient between two gas cells, through a photonic crystal fiber (PCF) surrounded by a furnace for temperature adjustment. PCF with 20-micron diameter affords physical space for gas-light interaction and provides a basis for gas viscosity measurement by determining the time for flow to exit a capillary tube under the influence of a pressure gradient. Infrared radiation from a diode laser is coupled into the fiber to be guided through the gas, and the light attenuation due to absorption from the molecular absorbing species is measured by a photo detector placed at the exit of the fiber. A numerical model from Sharipov and Graur describing local number density distribution in a unsteady state is applied for the determination of gas viscosity, based on the number density of gas measured by the absorption of the laser light, using the Beer-Lambert law. The measurement system is confirmed by measuring the viscosity of CO2 as a reference gas.

Towards building a robust computational framework to simulate multi-physics problems - a solution technique for three-phase (gas-liquid-solid) interactions

NASA Astrophysics Data System (ADS)

Zhang, Lucy

In this talk, we show a robust numerical framework to model and simulate gas-liquid-solid three-phase flows. The overall algorithm adopts a non-boundary-fitted approach that avoids frequent mesh-updating procedures by defining independent meshes and explicit interfacial points to represent each phase. In this framework, we couple the immersed finite element method (IFEM) and the connectivity-free front tracking (CFFT) method that model fluid-solid and gas-liquid interactions, respectively, for the three-phase models. The CFFT is used here to simulate gas-liquid multi-fluid flows that uses explicit interfacial points to represent the gas-liquid interface and for its easy handling of interface topology changes. Instead of defining different levels simultaneously as used in level sets, an indicator function naturally couples the two methods together to represent and track each of the three phases. Several 2-D and 3-D testing cases are performed to demonstrate the robustness and capability of the coupled numerical framework in dealing with complex three-phase problems, in particular free surfaces interacting with deformable solids. The solution technique offers accuracy and stability, which provides a means to simulate various engineering applications. The author would like to acknowledge the supports from NIH/DHHS R01-2R01DC005642-10A1 and the National Natural Science Foundation of China (NSFC) 11550110185.

21 CFR 868.1430 - Carbon monoxide gas analyzer.

Code of Federal Regulations, 2011 CFR

2011-04-01

... techniques such as infrared absorption or gas chromatography. (b) Classification. Class II (performance... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Carbon monoxide gas analyzer. 868.1430 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1430 Carbon monoxide gas analyzer. (a...

21 CFR 868.1430 - Carbon monoxide gas analyzer.

Code of Federal Regulations, 2010 CFR

2010-04-01

... techniques such as infrared absorption or gas chromatography. (b) Classification. Class II (performance... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Carbon monoxide gas analyzer. 868.1430 Section 868...) MEDICAL DEVICES ANESTHESIOLOGY DEVICES Diagnostic Devices § 868.1430 Carbon monoxide gas analyzer. (a...

Enhanced responses of the anterior cingulate cortex neurones to colonic distension in viscerally hypersensitive rats

PubMed Central

Gao, Jun; Wu, Xiaoyin; Owyang, Chung; Li, Ying

2006-01-01

The anterior cingulate cortex (ACC) is critically involved in processing the affective component of pain sensation. Visceral hypersensitivity is a characteristic of irritable bowel syndrome. Electrophysiological activity of the ACC with regard to visceral sensitization has not been characterized. Single ACC neuronal activities in response to colorectal distension (CRD) were recorded in control, sham-treated rats and viscerally hypersensitive (EA) rats (induced by chicken egg albumin injection, i.p). The ACC neurones of controls failed to respond to 10 or 30 mmHg CRD; only 22% were activated by 50 mmHg CRD. Among the latter, 16.4% exhibited an excitatory response to CRD and were labelled ‘CRD-excited’ neurones. In contrast, CRD (10, 30 and 50 mmHg) markedly increased ACC neuronal responses of EA rats (10%, 28% and 47%, respectively). CRD produced greater pressure-dependent increases in ACC spike firing rates in EA rats compared with controls. Splanchnicectomy combined with pelvic nerve section abolished ACC responses to CRD in EA rats. Spontaneous activity in CRD-excited ACC neurones was significantly higher in EA rats than in controls. CRD-excited ACC neurones in control and EA rats (7 of 16 (42%) and 8 of 20 (40%), respectively) were activated by transcutaneous electrical and thermal stimuli. However, ACC neuronal activity evoked by noxious cutaneous stimuli did not change significantly in EA rats. This study identifies CRD-responsive neurones in the ACC and establishes for the first time that persistence of a heightened visceral afferent nociceptive input to the ACC induces ACC sensitization, characterized by increased spontaneous activity of CRD-excited neurones, decreased CRD pressure threshold, and increased response magnitude. Enhanced ACC nociceptive transmission in viscerally hypersensitive rats is restricted to visceral afferent input. PMID:16239277

Tailored ramp wave generation in gas gun experiments

NASA Astrophysics Data System (ADS)

Cotton, Matthew; Chapman, David; Winter, Ron; Harris, Ernie; Eakins, Daniel

2015-09-01

Gas guns are traditionally used as platforms to introduce a planar shock wave to a material using plate impact methods, generating states on the Hugoniot. The ability to deliver a ramp wave to a target during a gas gun experiment enables access to different regions of the equation-of-state surface, making it a valuable technique for characterising material behaviour. Previous techniques have relied on the use of multi-material impactors to generate a density gradient, which can be complex to manufacture. In this paper we describe the use of an additively manufactured steel component consisting of an array of tapered spikes which can deliver a ramp wave over ˜ 2 μs. The ability to tailor the input wave by varying the component design is discussed, an approach which makes use of the design freedom offered by additive manufacturing techniques to rapidly iterate the spike profile. Results from gas gun experiments are presented to evaluate the technique, and compared with 3D hydrodynamic simulations.

Extraction and evaluation of gas-flow-dependent features from dynamic measurements of gas sensors array

NASA Astrophysics Data System (ADS)

Kalinowski, Paweł; Woźniak, Łukasz; Jasiński, Grzegorz; Jasiński, Piotr

2016-11-01

Gas analyzers based on gas sensors are the devices which enable recognition of various kinds of volatile compounds. They have continuously been developed and investigated for over three decades, however there are still limitations which slow down the implementation of those devices in many applications. For example, the main drawbacks are the lack of selectivity, sensitivity and long term stability of those devices caused by the drift of utilized sensors. This implies the necessity of investigations not only in the field of development of gas sensors construction, but also the development of measurement procedures or methods of analysis of sensor responses which compensate the limitations of sensors devices. One of the fields of investigations covers the dynamic measurements of sensors or sensor-arrays response with the utilization of flow modulation techniques. Different gas delivery patterns enable the possibility of extraction of unique features which improves the stability and selectivity of gas detecting systems. In this article three utilized flow modulation techniques are presented, together with the proposition of the evaluation method of their usefulness and robustness in environmental pollutants detecting systems. The results of dynamic measurements of an commercially available TGS sensor array in the presence of nitrogen dioxide and ammonia are shown.

Soil gas screening for chlorinated solvents at three contaminated karst sites in Tennessee

USGS Publications Warehouse

Wolfe, W.J.; Williams, S.D.

2002-01-01

Soil gas was sampled using active sampling techniques and passive collectors at three sites in Tennessee to evaluate the effectiveness of these techniques for locating chlorinated solvent sources and flowpaths in karst aquifers. Actively collected soil gas samples were analyzed in the field with a portable gas chromatograph, and the passive soil gas collectors were analyzed in the lab with gas chromatography/mass spectrometry. Results of the sampling indicate that the effectiveness of both techniques is highly dependent on the distribution of the contaminants in the subsurface, the geomorphic and hydrogeologic characteristics of the site, and, in one case, on seasonal conditions. Both active and passive techniques identified areas of elevated subsurface chlorinated solvent concentrations at a landfill site where contamination remains concentrated in the regolith. Neither technique detected chlorinated solvents known to be moving in the bedrock at a manufacturing site characterized by thick regolith and an absence of surficial karst features. Passive soil gas sampling had varied success detecting flowpaths for chloroform in the bedrock at a train derailment site characterized by shallow regolith and abundant surficial karst features. At the train derailment site, delineation of the contaminant flowpath through passive soil gas sampling was stronger and more detailed under Winter conditions than summer.

Real-time detection of dielectric anisotropy or isotropy in unconventional oil-gas reservoir rocks supported by the oblique-incidence reflectivity difference technique

PubMed Central

Zhan, Honglei; Wang, Jin; Zhao, Kun; Lű, Huibin; Jin, Kuijuan; He, Liping; Yang, Guozhen; Xiao, Lizhi

2016-01-01

Current geological extraction theory and techniques are very limited to adequately characterize the unconventional oil-gas reservoirs because of the considerable complexity of the geological structures. Optical measurement has the advantages of non-interference with the earth magnetic fields, and is often useful in detecting various physical properties. One key parameter that can be detected using optical methods is the dielectric permittivity, which reflects the mineral and organic properties. Here we reported an oblique-incidence reflectivity difference (OIRD) technique that is sensitive to the dielectric and surface properties and can be applied to characterization of reservoir rocks, such as shale and sandstone core samples extracted from subsurface. The layered distribution of the dielectric properties in shales and the uniform distribution in sandstones are clearly identified using the OIRD signals. In shales, the micro-cracks and particle orientation result in directional changes of the dielectric and surface properties, and thus, the isotropy and anisotropy of the rock can be characterized by OIRD. As the dielectric and surface properties are closely related to the hydrocarbon-bearing features in oil-gas reservoirs, we believe that the precise measurement carried with OIRD can help in improving the recovery efficiency in well-drilling process. PMID:27976746

Progress of gas-insulated transformers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Togawa, Y.; Ikeda, M.; Toda, K.

The world`s first transformer was manufactured at Ganz in Hungary in 1885. Two years later in 1887 patents applications were made for about oil immersed transformers in the US. Since then, oil immersed types have predominated for medium- and large-capacity transformers, which are now giving way to gas insulated transformers in some areas. Behind such trends are plans to construct substations inside buildings or underground, because of the difficulty in acquiring land for substations in large cities where power demand is concentrated. Requirements are protection against accidents, compactness and overall economy. Total gas insulated substations combining GIS units and gasmore » insulated transformers these needs. Demand for gas insulated transformers has been increasing rapidly, particularly in Japan and Hong Kong. First, relatively small-capacity models below 20--30 MVA were put into practical use and today 275 kV, 300 MVa models are in use and 500kV, 1,500 MVA models are coming into use. Engineering is progressing very rapidly in these areas. This paper describes the design techniques and important maintenance techniques for the latest gas insulated transformers from 5,000 kVA to 300 MVA.« less

Development of a Molecular Tagging Velocimetry Technique for Non-Intrusive Velocity Measurements in Low-Speed Gas Flows

NASA Technical Reports Server (NTRS)

Andre, M. A.; Bardet, P. M.; Cadell, S. R.; Woods, B.; Burns, R. A.; Danehy, P. M.

2017-01-01

N2O molecular tagging velocimetry (N2O-MTV) is developed for use in very-high-temperature reactor environments. Tests were carried out to determine the optimum excitation wavelength, tracer concentration, and timing parameters for the laser system. Using NO tracers obtained from photo-dissociation of N2O, velocity profiles are successfully obtained in air, nitrogen, and helium for a large range of parameters: temperature from 295 to 781 K, pressure from 1 to 3 bars, with a velocity precision of 0.01 m/s. Furthermore, by using two read pulses at adjustable time delays, the velocity dynamic range can be increased. An unprecedented dynamic range of 5,000 has been obtained to successfully resolve the flow during a helium blowdown from 1000 m/s down to 0.2 m/s. This technique is also applied to the high-temperature test facility (HTTF) at Oregon State University (OSU) during a depressurized condition cooldown (DCC) event. Details of these measurements are presented in a companion paper. This technique shows a strong potential for fundamental understanding of gas flows in nuclear reactors and to provide benchmark experimental data to validate numerical simulations.

Analysis of Low-Pressure Gas-Phase Pyrolytic Reactions by Mass Spectrometric Techniques,

DTIC Science & Technology

1989-01-01

temperatures and pressures known only as a polymeric substance, is similarly obtained in high purity by heating the polymer to its melting point (105-110’ C...filaments for Curie- point pyrolysis’ J.Anal.Appl.Pyrolysis. 5 (1983) 1-7 (with Helge Egsgaard) 4) ’Heterogeneous catalysis in gas phase reactions studied...by Curie- point pyrolysis. Gas phase pyrolysis of methyl dithio- acetat’ J.Anal.Appl.Pyrolysis. 5 (1983) 257-259 (with Helge Egsgaard) 5) ’Continuous

A simple technique for continuous measurement of time-variable gas transfer in surface waters

USGS Publications Warehouse

Tobias, Craig R.; Bohlke, John Karl; Harvey, Judson W.; Busenberg, Eurybiades

2009-01-01

Mass balance models of dissolved gases in streams, lakes, and rivers serve as the basis for estimating wholeecosystem rates for various biogeochemical processes. Rates of gas exchange between water and the atmosphere are important and error-prone components of these models. Here we present a simple and efficient modification of the SF6 gas tracer approach that can be used concurrently while collecting other dissolved gas samples for dissolved gas mass balance studies in streams. It consists of continuously metering SF6-saturated water directly into the stream at a low rate of flow. This approach has advantages over pulse injection of aqueous solutions or bubbling large amounts of SF6 into the stream. By adding the SF6 as a saturated solution, we minimize the possibility that other dissolved gas measurements are affected by sparging and/or bubble injecta. Because the SF6 is added continuously we have a record of changing gas transfer velocity (GTV) that is contemporaneous with the sampling of other nonconservative ambient dissolved gases. Over a single diel period, a 30% variation in GTV was observed in a second-order stream (Sugar Creek, Indiana, USA). The changing GTV could be attributed in part to changes in temperature and windspeed that occurred on hourly to diel timescales.

Requirements, techniques, and costs for contaminant removal from landfill gas.

PubMed

Kuhn, John N; Elwell, Anthony C; Elsayed, Nada H; Joseph, Babu

2017-05-01

Waste-to-energy projects are an increasingly prominent component of future energy portfolios. Landfill gas (LFG)-to-energy (LFGTE) projects are particularly important as they address greenhouse gas emissions. Contaminants in LFG may hamper these projects both from environmental and economic standpoints. The purpose of this review is to highlight key aspects (LFG composition ranges, LFG flowrates, and allowable tolerances for LFGTE technologies, performance and costs for contaminant removal by adsorption). Removal of key contaminants, H 2 S and siloxanes, by adsorption are surveyed in terms of adsorption capacities and regeneration abilities. Based on the open literature, costing analyses are tabulated and discussed. The findings indicate economics of contaminant removal depend heavily on the feed concentrations of contaminants, allowable tolerances for the LFGTE technology, and the current market for the product. Key trends, identification of challenges, and general purification guidelines for purifying LFG for energy projects are also discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Simple Techniques For Assessing Impacts Of Oil And Gas Operations On Public Lands: A Field Evaluation Of A Photoionization Detector (PID) At A Condensate Release Site, Padre Island National Seashore, Texas

USGS Publications Warehouse

Otton, James K.; Zielinski, Robert A.

2001-01-01

Simple, cost-effective techniques are needed for land managers to assess the environmental impacts of oil and gas production activities on public lands, so that sites may be prioritized for remediation or for further, more formal assessment. Field-portable instruments provide real-time data and allow the field investigator to extend an assessment beyond simply locating and mapping obvious disturbances. Field investigators can examine sites for the presence of hydrocarbons in the subsurface using a soil auger and a photoionization detector (PID). The PID measures volatile organic compounds (VOC) in soil gases. This allows detection of hydrocarbons in the shallow subsurface near areas of obvious oil-stained soils, oil in pits, or dead vegetation. Remnants of a condensate release occur in sandy soils at a production site on the Padre Island National Seashore in south Texas. Dead vegetation had been observed by National Park Service personnel in the release area several years prior to our visit. The site is located several miles south of the Malaquite Beach Campground. In early 2001, we sampled soil gases for VOCs in the area believed to have received the condensate. Our purpose in this investigation was: 1) to establish what sampling techniques might be effective in sandy soils with a shallow water and contrast them with techniques used in an earlier study; and 2) delineate the probable area of condensate release. Our field results show that sealing the auger hole with a clear, rigid plastic tube capped at the top end and sampling the soil gas through a small hole in the cap increases the soil VOC gas signature, compared to sampling soil gases in the bottom of an open hole. This sealed-tube sampling method increases the contrast between the VOC levels within a contaminated area and adjacent background areas. The tube allows the PID air pump to draw soil gas from the volume of soil surrounding the open hole below the tube in a zone less influenced by atmospheric air

The Noble Gas Fingerprint in a UK Unconventional Gas Reservoir

NASA Astrophysics Data System (ADS)

McKavney, Rory; Gilfillan, Stuart; Györe, Domokos; Stuart, Fin

2016-04-01

In the last decade, there has been an unprecedented expansion in the development of unconventional hydrocarbon resources. Concerns have arisen about the effect of this new industry on groundwater quality, particularly focussing on hydraulic fracturing, the technique used to increase the permeability of the targeted tight shale formations. Methane contamination of groundwater has been documented in areas of gas production1 but conclusively linking this to fugitive emissions from unconventional hydrocarbon production has been controversial2. A lack of baseline measurements taken before drilling, and the equivocal interpretation of geochemical data hamper the determination of possible contamination. Common techniques for "fingerprinting" gas from discrete sources rely on gas composition and isotopic ratios of elements within hydrocarbons (e.g. δ13CCH4), but the original signatures can be masked by biological and gas transport processes. The noble gases (He, Ne, Ar, Kr, Xe) are inert and controlled only by their physical properties. They exist in trace quantities in natural gases and are sourced from 3 isotopically distinct environments (atmosphere, crust and mantle)3. They are decoupled from the biosphere, and provide a separate toolbox to investigate the numerous sources and migration pathways of natural gases, and have found recent utility in the CCS4 and unconventional gas5 industries. Here we present a brief overview of noble gas data obtained from a new coal bed methane (CBM) field, Central Scotland. We show that the high concentration of helium is an ideal fingerprint for tracing fugitive gas migration to a shallow groundwater. The wells show variation in the noble gas signatures that can be attributed to differences in formation water pumping from the coal seams as the field has been explored for future commercial development. Dewatering the seams alters the gas/water ratio and the degree to which noble gases degas from the formation water. Additionally the

Multiplex gas chromatography: an alternative concept for gas chromatographic analysis of planetary atmospheres

NASA Technical Reports Server (NTRS)

Valentin, J. R.

1989-01-01

Gas chromatography (GC) is a powerful technique for analyzing gaseous mixtures. Applied to the earth's atmosphere, GC can be used to determine the permanent gases--such as carbon dioxide, nitrogen, and oxygen--and to analyze organic pollutants in air. The U.S. National Aeronautics and Space Administration (NASA) has used GC in spacecraft missions to Mars (the Viking Biology Gas Exchange Experiment [GEX] and the Viking Gas Chromatograph-Mass Spectrometer [GC-MS]) and to Venus (the Pioneer Venus Gas Chromatograph [PVGC] on board the Pioneer Venus sounder probe) for determining the atmospheric constituents of these two planets. Even though conventional GC was very useful in the Viking and Pioneer missions, spacecraft constraints and limitations intrinsic to the technique prevented the collection of more samples. With the Venus probe, for instance, each measurement took a relatively long time to complete (10 min), and successive samples could not be introduced until the previous samples had left the column. Therefore, while the probe descended through the Venusian atmosphere, only three samples were acquired at widely separated altitudes. With the Viking mission, the sampling rate was not a serious problem because samples were acquired over a period of one year. However, the detection limit was a major disadvantage. The GC-MS could not detect simple hydrocarbons and simple alcohols below 0.1 ppm, and the GEX could not detect them below 1 ppm. For more complex molecules, the detection limits were at the parts-per-billion level for both instruments. Finally, in both the Viking and Pioneer missions, the relatively slow rate of data acquisition limited the number of analyses, and consequently, the amount of information returned. Similar constraints are expected in future NASA missions. For instance, gas chromatographic instrumentation is being developed to collect and analyze organic gases and aerosols in the atmosphere of Titan (one of Saturn's satellites). The Titan

Measurement techniques and applications of charge transfer to aerospace research

NASA Technical Reports Server (NTRS)

Smith, A.

1978-01-01

A technique of developing high-velocity low-intensity neutral gas beams for use in aerospace research problems is described. This technique involves ionization of gaseous species with a mass spectrometer and focusing the resulting primary ion beam into a collision chamber containing a static gas at a known pressure and temperature. Equations are given to show how charge-transfer cross sections are obtained from a total-current measurement technique. Important parameters are defined for the charge-transfer process.

Optical control and diagnostics sensors for gas turbine machinery

NASA Astrophysics Data System (ADS)

Trolinger, James D.; Jenkins, Thomas P.; Heeg, Bauke

2012-10-01

There exists a vast range of optical techniques that have been under development for solving complex measurement problems related to gas-turbine machinery and phenomena. For instance, several optical techniques are ideally suited for studying fundamental combustion phenomena in laboratory environments. Yet other techniques hold significant promise for use as either on-line gas turbine control sensors, or as health monitoring diagnostics sensors. In this paper, we briefly summarize these and discuss, in more detail, some of the latter class of techniques, including phosphor thermometry, hyperspectral imaging and low coherence interferometry, which are particularly suited for control and diagnostics sensing on hot section components with ceramic thermal barrier coatings (TBCs).

Frontal Mucocele Extended Orbita and Endoscopic Marsupialization Technique.

PubMed

Erdogan, Banu Atalay; Unlu, Nazmiye; Aydin, Sedat; Avci, Hakan

2018-06-01

Mucocele is benign, slow-growing, mucous-filled cystic lesions that arise in the paranasal sinuses. It causes progressive distension of the bony walls and induces compressive symptoms. Surgical treatment of paranasal sinus mucoceles includes endoscopic approach or external approach. The authors report a patient of frontal mucocele who presented with a history of progressive unilateral protrusion. Computed tomography scan revealed a large mucocele of the frontal sinus with orbital extension on the same side. He was successfully treated with endoscopic marsupialization without any serious complications.

A shock capturing technique for hypersonic, chemically relaxing flows

NASA Technical Reports Server (NTRS)

Eberhardt, S.; Brown, K.

1986-01-01

A fully coupled, shock capturing technique is presented for chemically reacting flows at high Mach numbers. The technique makes use of a total variation diminishing (TVD) dissipation operator which results in sharp, crisp shocks. The eigenvalues and eigenvectors of the fully coupled system, which includes species conversion equations in addition to the gas dynamics equations, are analytically derived for a general reacting gas. Species production terms for a model dissociating gas are introduced and are included in the algorithm. The convective terms are solved using a first-order TVD scheme while the source terms are solved using a fourth-order Runge-Kutta scheme to enhance stability. Results from one-dimensional numerical experiments are shown for a two species and a three species gas.

Methods and techniques for measuring gas emissions from agricultural and animal feeding operations.

PubMed

Hu, Enzhu; Babcock, Esther L; Bialkowski, Stephen E; Jones, Scott B; Tuller, Markus

2014-01-01

Emissions of gases from agricultural and animal feeding operations contribute to climate change, produce odors, degrade sensitive ecosystems, and pose a threat to public health. The complexity of processes and environmental variables affecting these emissions complicate accurate and reliable quantification of gas fluxes and production rates. Although a plethora of measurement technologies exist, each method has its limitations that exacerbate accurate quantification of gas fluxes. Despite a growing interest in gas emission measurements, only a few available technologies include real-time, continuous monitoring capabilities. Commonly applied state-of-the-art measurement frameworks and technologies were critically examined and discussed, and recommendations for future research to address real-time monitoring requirements for forthcoming regulation and management needs are provided.

[Set-up, portals and normal exploration in wrist arthroscopy].

PubMed

Atzei, A; Luchetti, R; Sgarbossa, A; Carità, E; Llusà, M

2006-11-01

Arthroscopy is an accepted technique for evaluation of intra-articular pathology and treatment of a variety of disorders even in the wrist joint. Dedicated miniaturized instrumentation is needed along with a specific traction system. The external distraction alone (dry technique) allows for complete joint exploration and several type of arthroscopic surgery, avoiding annoying leaking in the subcutaneous tissues, though further distension of the articular pouches can be achieved by saline infusion (fluid distension or wet technique). Knowledge of surface anatomic landmarks and careful surgical technique are required for proper portal placement and in order to avoid injury to the numerous noble structures crossing nearby. Description of radio- and medio-carpal portals is provided along with the different bony, condral, synovial and ligamentous structures that can be visualised or treated through each portal. Surgeon can choose the most suitable portal for scope or instruments, according to specific needs for diagnostic or therapeutic purposes.

[Set-up, portals and normal exploration in wrist arthroscopy.

PubMed

Atzei, A; Luchetti, R; Sgarbossa, A; Carità, E; Llusà, M

2006-11-01

Arthroscopy is an accepted technique for evaluation of intra-articular pathology and treatment of a variety of disorders even in the wrist joint. Dedicated miniaturized instrumentation is needed along with a specific traction system. The external distraction alone (dry technique) allows for complete joint exploration and several type of arthroscopic surgery, avoiding annoying leaking in the subcutaneous tissues, though further distension of the articular pouches can be achieved by saline infusion (fluid distension or wet technique). Knowledge of surface anatomic landmarks and careful surgical technique are required for proper portal placement and in order to avoid injury to the numerous noble structures crossing nearby. Description of radio- and medio-carpal portals is provided along with the different bony, condral, synovial and ligamentous structures that can be visualised or treated through each portal. Surgeon can choose the most suitable portal for scope or instruments, according to specific needs for diagnostic or therapeutic purposes.

Seismic imaging of gas hydrate reservoir heterogeneities

NASA Astrophysics Data System (ADS)

Huang, Jun-Wei

Natural gas hydrate, a type of inclusion compound or clathrate, are composed of gas molecules trapped within a cage of water molecules. The presence of gas hydrate has been confirmed by core samples recovered from boreholes. Interests in the distribution of natural gas hydrate stem from its potential as a future energy source, geohazard to drilling activities and their possible impact on climate change. However the current geophysical investigations of gas hydrate reservoirs are still too limited to fully resolve the location and the total amount of gas hydrate due to its complex nature of distribution. The goal of this thesis is twofold, i.e., to model (1) the heterogeneous gas hydrate reservoirs and (2) seismic wave propagation in the presence of heterogeneities in order to address the fundamental questions: where are the location and occurrence of gas hydrate and how much is stored in the sediments. Seismic scattering studies predict that certain heterogeneity scales and velocity contrasts will generate strong scattering and wave mode conversion. Vertical Seismic Profile (VSP) techniques can be used to calibrate seismic characterization of gas hydrate expressions on surface seismograms. To further explore the potential of VSP in detecting the heterogeneities, a wave equation based approach for P- and S-wave separation is developed. Tests on synthetic data as well as applications to field data suggest alternative acquisition geometries for VSP to enable wave mode separation. A new reservoir modeling technique based on random medium theory is developed to construct heterogeneous multi-variable models that mimic heterogeneities of hydrate-bearing sediments at the level of detail provided by borehole logging data. Using this new technique, I modeled the density, and P- and S-wave velocities in combination with a modified Biot-Gassmann theory and provided a first order estimate of the in situ volume of gas hydrate near the Mallik 5L-38 borehole. Our results suggest a

Fast, Nonspattering Inert-Gas Welding

NASA Technical Reports Server (NTRS)

Gilbert, Jeffrey L.

1991-01-01

Proposed welding technique combines best features of metal (other than tungsten)/inert-gas welding, plasma arc welding, and tungsten/inert-gas welding. Advantages include: wire fed to weld joint preheated, therefore fed at high speed without spattering; high-frequency energy does not have to be supplied to workpiece to initiate welding; size of arc gap not critical, power-supply control circuit adjusts voltage across gap to compensate for changes; only low gas-flow rate needed; welding electrode replaced easily as prefabricated assembly; external wire-feeding manipulator not needed; and welding process relatively forgiving of operator error.

Laser Spinning: A New Technique for Nanofiber Production

NASA Astrophysics Data System (ADS)

Penide, J.; Quintero, F.; del Val, J.; Comesaña, R.; Lusquiños, F.; Riveiro, A.; Pou, J.

Laser Spinning is a new technique to produce ultralongnanofibers with tailored chemical compositions. In this method, a high power laser is employed to melt a small volume of the precursor material at high temperatures. At the same time, a supersonic gas jet is injected on this molten volume producing its rapid cooling and elongation by viscous friction with the high speed gas flow, hence forming the amorphous nanofibers. This paper collects the main results obtained since the introduction of this technique in 2007.

Comparison of Techniques for Non-Intrusive Fuel Drop Size Measurements in a Subscale Gas Turbine Combustor

NASA Technical Reports Server (NTRS)

Zaller, Michelle; Anderson, Robert C.; Hicks, Yolanda R.; Locke, Randy J.

1999-01-01

In aviation gas turbine combustors, many factors, such as the degree and extent of fuel/air mixing and fuel vaporization achieved prior to combustion, influence the formation of undesirable pollutants. To assist in analyzing the extent of fuel/air mixing, flow visualization techniques have been used to interrogate the fuel distributions during subcomponent tests of lean-burning fuel injectors. Discrimination between liquid and vapor phases of the fuel was determined by comparing planar laser-induced fluorescence (PLIF) images, elastically-scattered light images, and phase/Doppler interferometer measurements. Estimates of Sauter mean diameters are made by ratioing PLIF and Mie scattered intensities for various sprays, and factors affecting the accuracy of these estimates are discussed. Mie calculations of absorption coefficients indicate that the fluorescence intensities of individual droplets are proportional to their surface areas, instead of their volumes, due to the high absorbance of the liquid fuel for the selected excitation wavelengths.

Biomechanical evaluation of various suture configurations in side-to-side tenorrhaphy.

PubMed

Wagner, Emilio; Ortiz, Cristian; Wagner, Pablo; Guzman, Rodrigo; Ahumada, Ximena; Maffulli, Nicola

2014-02-05

Side-to-side tenorrhaphy is increasingly used, but its mechanical performance has not been studied. Two porcine flexor digitorum tendon segments of equal length (8 cm) and thickness (1 cm) were placed side by side. Eight tenorrhaphies (involving sixteen tendons) were performed with each of four suture techniques (running locked, simple eight, vertical mattress, and pulley suture). The resulting constructs underwent cyclic loading on a tensile testing machine, followed by monotonically increasing tensile load if failure during cyclic loading did not occur. Clamps secured the tendons on each side of the repair, and specimens were mounted vertically. Cyclic loading varied between 15 N and 35 N, with a distension rate of 1 mm/sec. Cyclic loading strength was determined by applying a force of 70 N. The cause of failure and tendon distension during loading were recorded. All failures occurred in the monotonic loading phase and resulted from tendon stripping. No suture or knot failure was observed. The mean loads resisted by the configurations ranged from 138 to 398 N. The mean load to failure, maximum load resisted prior to 1 cm of distension, and load resisted at 1 cm of distension were significantly lower for the vertical mattress suture group than for any of the other three groups (p < 0.031). All four groups sustained loads well above the physiologic loads expected to occur in tendons in the foot and ankle (e.g., in tendon transfer for tibialis posterior tendon insufficiency). None of the four side-to-side configurations distended appreciably during the cyclic loading phase. The vertical mattress suture configuration appeared to be weaker than the other configurations. For surgeons who advocate immediate loading or motion of a side-to-side tendon repair, a pulley, running locked, or simple eight suture technique appears to provide a larger safety margin compared with a vertical mattress suture technique.

Reaction behavior of SO2 in the sintering process with flue gas recirculation.

PubMed

Yu, Zhi-Yuan; Fan, Xiao-Hui; Gan, Min; Chen, Xu-Ling; Chen, Qiang; Huang, Yun-Song

2016-07-01

The primary goal of this paper is to reveal the reaction behavior of SO2 in the sinter zone, combustion zone, drying-preheating zone, and over-wet zone during flue gas recirculation (FGR) technique. The results showed that SO2 retention in the sinter zone was associated with free-CaO in the form of CaSO3/CaSO4, and the SO2 adsorption reached a maximum under 900ºC. SO2 in the flue gas came almost from the combustion zone. One reaction behavior was the oxidation of sulfur in the sintering mix when the temperature was between 800 and 1000ºC; the other behavior was the decomposition of sulfite/sulfate when the temperature was over 1000ºC. However, the SO2 adsorption in the sintering bed mainly occurred in the drying-preheating zone, adsorbed by CaCO3, Ca(OH)2, and CaO. When the SO2 adsorption reaction in the drying-preheating zone reached equilibrium, the excess SO2 gas continued to migrate to the over-wet zone and was then absorbed by Ca(OH)2 and H2O. The emission rising point of SO2 moved forward in combustion zone, and the concentration of SO2 emissions significantly increased in the case of flue gas recirculation (FGR) technique. Aiming for the reuse of the sensible heat and a reduction in exhaust gas emission, the FGR technique is proposed in the iron ore sintering process. When using the FGR technique, SO2 emission in exhaust gas gets changed. In practice, the application of the FGR technique in a sinter plant should be cooperative with the flue gas desulfurization (FGD) technique. Thus, it is necessary to study the influence of the FGR technique on SO2 emissions because it will directly influence the demand and design of the FGD system.

An overview of aerospace gas turbine technology of relevance to the development of the automotive gas turbine engine

NASA Technical Reports Server (NTRS)

Evans, D. G.; Miller, T. J.

1978-01-01

Technology areas related to gas turbine propulsion systems with potential for application to the automotive gas turbine engine are discussed. Areas included are: system steady-state and transient performance prediction techniques, compressor and turbine design and performance prediction programs and effects of geometry, combustor technology and advanced concepts, and ceramic coatings and materials technology.

Multiplex gas chromatography for use in space craft

NASA Technical Reports Server (NTRS)

Valentin, J. R.

1985-01-01

Gas chromatography is a powerful technique for the analysis of gaseous mixtures. Some limitations in this technique still exist which can be alleviated with multiplex gas chromatography (MGC). In MGC, rapid multiple sample injections are made into the column without having to wait for one determination to be finished before taking a new sample. The resulting data must then be reduced using computational methods such as cross correlation. In order to efficiently perform multiplexgas chromatography, experiments in the laboratory and on board future space craft, skills, equipment, and computer software were developed. Three new techniques for modulating, i.e., changing, sample concentrations were demonstrated by using desorption, decomposition, and catalytic modulators. In all of them, the need for a separate gas stream as the carrier was avoided by placing the modulator at the head of the column to directly modulate a sample stream. Finally, the analysis of an environmental sample by multiplex chromatography was accomplished by employing silver oxide to catalytically modulate methane in ambient air.

3D motion picture of transparent gas flow by parallel phase-shifting digital holography

NASA Astrophysics Data System (ADS)

Awatsuji, Yasuhiro; Fukuda, Takahito; Wang, Yexin; Xia, Peng; Kakue, Takashi; Nishio, Kenzo; Matoba, Osamu

2018-03-01

Parallel phase-shifting digital holography is a technique capable of recording three-dimensional (3D) motion picture of dynamic object, quantitatively. This technique can record single hologram of an object with an image sensor having a phase-shift array device and reconstructs the instantaneous 3D image of the object with a computer. In this technique, a single hologram in which the multiple holograms required for phase-shifting digital holography are multiplexed by using space-division multiplexing technique pixel by pixel. We demonstrate 3D motion picture of dynamic and transparent gas flow recorded and reconstructed by the technique. A compressed air duster was used to generate the gas flow. A motion picture of the hologram of the gas flow was recorded at 180,000 frames/s by parallel phase-shifting digital holography. The phase motion picture of the gas flow was reconstructed from the motion picture of the hologram. The Abel inversion was applied to the phase motion picture and then the 3D motion picture of the gas flow was obtained.

Multimedia manuscript. Heller myotomy and intraluminal fundoplication: a NOTES technique.

PubMed

Perretta, Silvana; Dallemagne, Bernard; Allemann, Pierre; Alleman, Pierre; Marescaux, Jacques

2010-11-01

It is generally accepted that the most effective treatment of achalasia is a surgical myotomy. Nevertheless, if a myotomy alone is performed, reflux may occur in up to 30% of patients. The aim of this study was to explore a transoral incisionless stepwise approach to both esophageal Heller myotomy and fundoplication. The first step consisted of creating the esophageal myotomy. Under general anesthesia, with the pig supine, endoscopy was performed to assess the location of the esophagogastric junction (EGJ). The mucosa on the right posterolateral esophageal wall was cut with the needle-knife 15 cm above the lower esophageal sphincter (LES) and then dilated with blunt dissection to introduce the scope. A submucosal tunnel was created distally with CO(2) and blunt dissection. Once the gastroesophageal junction (GEJ) and the clasp fibers were identified, the muscular layer was cut. The scope was withdrawn into the lumen and the mucosal flap was sealed with endoscopic clips. The adequacy of the myotomy was evaluated using pre- and postoperative manometry and by comparing the EGJ distensibility before, during, and after the division of the esophageal muscular fibers using the functional lumen imaging probe, EndoFLIP®. The second step, consisted of building a transoral incisionless fundoplication 4 weeks postoperatively using the EsophyX™. Both Heller myotomy and endoscopic fundoplication were accomplished successfully with no injury to the esophageal mucosa. Postoperative manometry demonstrated a 50% loss in mean LES pressure (mean preoperative LES pressure = 22.2 mmHg; mean postoperative LES pressure = 10 mmHg, P < 0.005). The EndoFLIP® showed a preoperative minimal diameter of 6 mm with a cross-sectional area of 28 mm(2). Postoperatively, the junction was more compliant (minimal diameter = 15 mm; cross-sectional area = 177 mm(2)), with the main improvement in distensibility occurring when the clasps fibers were removed. A stepwise transoral incisionless approach to

A Gas Dynamics Method Based on The Spectral Deferred Corrections (SDC) Time Integration Technique and The Piecewise Parabolic Method (PPM)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samet Y. Kadioglu

2011-12-01

We present a computational gas dynamics method based on the Spectral Deferred Corrections (SDC) time integration technique and the Piecewise Parabolic Method (PPM) finite volume method. The PPM framework is used to define edge averaged quantities which are then used to evaluate numerical flux functions. The SDC technique is used to integrate solution in time. This kind of approach was first taken by Anita et al in [17]. However, [17] is problematic when it is implemented to certain shock problems. Here we propose significant improvements to [17]. The method is fourth order (both in space and time) for smooth flows,more » and provides highly resolved discontinuous solutions. We tested the method by solving variety of problems. Results indicate that the fourth order of accuracy in both space and time has been achieved when the flow is smooth. Results also demonstrate the shock capturing ability of the method.« less

A prospective single-institute study of the impact of Daikenchuto on the early postoperative outcome after living donor liver transplantation.

PubMed

Takatsuki, Mitsuhisa; Hidaka, Masaaki; Soyama, Akihiko; Hara, Takanobu; Okada, Satomi; Ono, Shinichiro; Adachi, Tomohiko; Eguchi, Susumu

2018-01-20

The aim of this study was to investigate the impact of Daikenchuto (DKT) on early postoperative outcomes after living donor liver transplantation (LDLT), focusing on the prevention of abdominal distension and bacterial translocation. Adult LDLT recipients were prospectively divided into 2 groups, who were administered DKT (n = 20, group A) or not (n = 20, group B). The area of bowel gas defined as gas volume score (GVS) 7 days after LDLT was calculated. Postoperative liver function tests, the development of bacterial, viral, and fungal infections, and GVS after LDLT were reviewed. There were no significant differences in liver function tests and ammonia level after LDLT. Also, the rates of infection and the result of culture study were not different between groups. The median GVS 7 days after LDLT was not significantly different between groups A (0.26 (range, 0.12-0.58)) and B (0.23 (range, 0.15-0.42)). No positive impact was observed for 14-day DKT administration after LDLT, in terms of preventing infection or abdominal distension. Copyright © 2018. Published by Elsevier Taiwan.

Arthroscopic Revision Surgery for Failure of Open Latarjet Technique.

PubMed

Cuéllar, Adrián; Cuéllar, Ricardo; de Heredia, Pablo Beltrán

2017-05-01

To evaluate the efficacy in treating pain, limited range of motion, and continued instability of the Latarjet open technique via the use of arthroscopy. A retrospective review of patients who underwent arthroscopic capsule plication after failure of an open Latarjet technique was performed. Revision surgery was indicated in cases of recurrent instability and associated pain. Only patients with a glenoid defect <25% were considered. The Constant and Rowe scores were administered, whereas pain was assessed with a visual analog scale before the reoperation and at 24 months after operation. Radiographs, computed tomography, and CT arthrography scans were performed. Twelve patients met the inclusion criteria. All patients had capsular distension and consequently were subjected to a capsuloplasty. Shoulder function, stability, and pain had all improved significantly at 24 months after arthroscopic revision (P < .0001). In particular, the Constant score increased from 44.9 (standard deviation [SD] 7.10) to 89.3 (SD 12.6) points, the Rowe score improved from 49.5 (SD 10.1) to 80.9 (SD 10.9), whereas the visual analog scale pain score decreased from 6.75 (SD 1.17) to 1.38 (SD 1.06). Primary open Latarjet with a glenoid bone defect <25% that failed due to capsular redundancy is amenable to successful treatment with arthroscopic capsuloplasty. Arthroscopic approaches can offer a good solution for treating previously failed open Latarjet procedures. Level IV, therapeutic case series. Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Technique for the control of the crystal habit of ultrafine particles in the gas-evaporation technique

NASA Astrophysics Data System (ADS)

Kasukabe, S.; Mihama, K.

1986-12-01

Magnesium ultrafine particles have clear-cut habits such as hexagonal plates and polyhedra. When magnesium is evaporated downwards using a tube with holes at the bottom, hexagonal plates are formed exclusively throughout the smoke. Their size is controlled by selecting an inert gas. The growth process of an hexagonal plate can be considered to be a coalescent growth of other hexagonal plates.

A prospective, randomized, double-blind, placebo-controlled parallel-group dual site trial to evaluate the effects of a Bacillus coagulans-based product on functional intestinal gas symptoms.

PubMed

Kalman, Douglas S; Schwartz, Howard I; Alvarez, Patricia; Feldman, Samantha; Pezzullo, John C; Krieger, Diane R

2009-11-18

This randomized double blind placebo controlled dual site clinical trial compared a probiotic dietary supplement to placebo regarding effects on gastrointestinal symptoms in adults with post-prandial intestinal gas-related symptoms (abdominal pain, distention, flatulence) but no gastrointestinal (GI) diagnoses to explain the symptoms. Sixty-one adults were enrolled (age 36.5 +/- 12.6 years; height 165.1 +/- 9.2 cm; weight 75.4 +/- 17.3 kg) and randomized to either Digestive Advantage Gas Defense Formula - (GanedenBC30 Bacillus coagulans GBI-30, 6086): n = 30; or Placebo: n = 31. Study subjects were evaluated every two weeks over a four-week period using validated questionnaires and standard biochemical safety testing. Outcome criteria of interest included change from baseline in Gastrointestinal Symptom Rating Scale (GSRS) abdominal pain, abdominal distention, flatus, and the Severity of Dyspepsia Assessment (SODA) bloating and gas subscores over four weeks of product use. Measured against the placebo, subjects in the probiotic group achieved significant improvements in GSRS abdominal pain subscore (p = 0.046) and the GSRS total score (p = 0.048), with a strong trend for improvement on the GSRS abdominal distension subscore (p = 0.061). A strong placebo effect was evident which could explain the lack of statistical significant differences between the groups for many of the efficacy variables. In conclusion, the Bacillus coagulans-based product was effective in improving the quality of life and reducing gastrointestinal symptoms in adults with post prandial intestinal gas-related symptoms and no GI diagnoses. ClinicalTrials.gov Identifier: NCT00881322.

A prospective, randomized, double-blind, placebo-controlled parallel-group dual site trial to evaluate the effects of a Bacillus coagulans-based product on functional intestinal gas symptoms

PubMed Central

2009-01-01

Background This randomized double blind placebo controlled dual site clinical trial compared a probiotic dietary supplement to placebo regarding effects on gastrointestinal symptoms in adults with post-prandial intestinal gas-related symptoms (abdominal pain, distention, flatulence) but no gastrointestinal (GI) diagnoses to explain the symptoms. Methods Sixty-one adults were enrolled (age 36.5 ± 12.6 years; height 165.1 ± 9.2 cm; weight 75.4 ± 17.3 kg) and randomized to either Digestive Advantage™ Gas Defense Formula - (GanedenBC30 Bacillus coagulans GBI-30, 6086): n = 30; or Placebo: n = 31. Study subjects were evaluated every two weeks over a four-week period using validated questionnaires and standard biochemical safety testing. Outcome criteria of interest included change from baseline in Gastrointestinal Symptom Rating Scale (GSRS) abdominal pain, abdominal distention, flatus, and the Severity of Dyspepsia Assessment (SODA) bloating and gas subscores over four weeks of product use. Results Measured against the placebo, subjects in the probiotic group achieved significant improvements in GSRS abdominal pain subscore (p = 0.046) and the GSRS total score (p = 0.048), with a strong trend for improvement on the GSRS abdominal distension subscore (p = 0.061). A strong placebo effect was evident which could explain the lack of statistical significant differences between the groups for many of the efficacy variables. Conclusion In conclusion, the Bacillus coagulans-based product was effective in improving the quality of life and reducing gastrointestinal symptoms in adults with post prandial intestinal gas-related symptoms and no GI diagnoses. Trial Registration ClinicalTrials.gov Identifier: NCT00881322 PMID:19922649

Ion plating technique improves thin film deposition

NASA Technical Reports Server (NTRS)

Mattox, D. M.

1968-01-01

Ion plating technique keeps the substrate surface clean until the film is deposited, allows extensive diffusion and chemical reaction, and joins insoluble or incompatible materials. The technique involves the deposition of ions on the substrate surface while it is being bombarded with inert gas ions.

Indirect Gas Species Monitoring Using Tunable Diode Lasers

DOEpatents

Von Drasek, William A.; Saucedo, Victor M.

2005-02-22

A method for indirect gas species monitoring based on measurements of selected gas species is disclosed. In situ absorption measurements of combustion species are used for process control and optimization. The gas species accessible by near or mid-IR techniques are limited to species that absorb in this spectral region. The absorption strength is selected to be strong enough for the required sensitivity and is selected to be isolated from neighboring absorption transitions. By coupling the gas measurement with a software sensor gas, species not accessible from the near or mid-IR absorption measurement can be predicted.

Experimental and numerical test of the micrometeorological mass difference technique for the measurement of trace gas emissions from small plots.

PubMed

Magliulo, Vincenzo; Alterio, Giovanni; Peressotti, Alessandro

2004-05-01

Micrometeorological methods for measuring fluxes of gases between the land surface and the atmosphere are non-invasive: in fact, they do not interfere with natural processes of gas exchange. The Micrometeorological Mass Difference (MMD) approach can be used for many environmental monitoring purposes, such as to measure methane and carbon dioxide emission from landfills, methane production by grazing animals, trace gas emission from waste products and from agricultural soils, photosynthesis, and transpiration of plant canopies. The purpose of this study is to adapt the MMD technique, originally developed in Australia, to monitor CO2 and trace gases exchange rate at the plot level. Comparison of different treatments in replicated experiments requires plots of few rather than tens of meters. The tests reported here were performed on a square area (4 m x 4 m) in the meteorological field of the experimental farm of CNR-ISAFOM located in Vitulazio, province of Caserta, Italy (40 degrees 07' N, 14 degrees 50' E, 25 m above sea level) and consisted of the release of pure CO2 at different rates (1.7, 1.3, 0.6 L min(-1)) from a single source on the ground in the center of the experimental area and the consequent measurement of the environmental variables (wind speed and direction, CO2 concentration) at different times at four heights (up to 1.2 m) in order to compute the mass balance according to MMD technique. Measured flow rates well accounted for the mass of CO2 released. A flow underestimation occurred when wind speed dropped below 1.5 m s(-1), in accord with the previous findings obtained in Australia: this happened because anemometers can stall at low speeds, and their measurements are unreliable and because of significant loss of mass from the top of the apparatus. The experimental results were compared with outputs of Computational Fluid Dynamic (CFD) simulations. The commercial CFD package Fluent was used to evaluate performances and sources of errors. According to

Unusual high B{sub s} for Fe-based amorphous powders produced by a gas-atomization technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshida, K.; Bito, M.; Kageyama, J.

2016-05-15

Fe-based alloy powders with a high Fe content of about 81 at.% were produced by a gas-atomization technique. Powders of Fe{sub 81}Si{sub 1.9}B{sub 5.7}P{sub 11.4} (at.%) alloy showed a good glass forming ability and exhibited unusual high saturation magnetic flux density of 1.57 T. The core-loss property at a frequency of 100 kHz for the compacted core made of the Fe{sub 81}Si{sub 1.9}B{sub 5.7}P{sub 11.4} powder is evaluated to be less than 500 kW/m{sup 3} under a maximum induction of 100 mT. Moreover, good DC-superposition characteristic of the core was also confirmed. These results suggest that the present Fe-based alloymore » powder is promising for low-loss magnetic-core materials and expected to contribute in miniaturization of electric parts in the near future.« less

An application of digital image processing techniques to the characterization of liquid petroleum gas (LPG) spray

NASA Astrophysics Data System (ADS)

Qi, Y. L.; Xu, B. Y.; Cai, S. L.

2006-12-01

To control fuel injection, optimize combustion and reduce emissions for LPG (liquefied petroleum gas) engines, it is necessary and important to understand the characteristics of LPG sprays. The present work investigates the geometry of LPG sprays, including spray tip penetration, spray angle, projected spray area and spray volume, by using schlieren photography and digital image processing techniques. Two types of single nozzle injectors were studied, with the same nozzle diameter, but one with and one without a double-hole flow-split head. A code developed to analyse the results directly from the digitized images is shown to be more accurate and efficient than manual measurement and analysis. Test results show that a higher injection pressure produces a longer spray tip penetration, a larger projected spray area and spray volume, but a smaller spray cone angle. The injector with the double-hole split-head nozzle produces better atomization and shorter tip penetration at medium and late injection times, but longer tip penetration in the early stage.

Conversion of laser energy to gas kinetic energy

NASA Technical Reports Server (NTRS)

Caledonia, G. E.

1976-01-01

Techniques for the gas phase absorption of laser radiation for ultimate conversion to gas kinetic energy are discussed. Particular emphasis is placed on absorption by the vibration rotation bands of diatomic molecules at high pressures. This high pressure absorption appears to offer efficient conversion of laser energy to gas translational energy. Bleaching and chemical effects are minimized and the variation of the total absorption coefficient with temperature is minimal.

A low tritium hydride bed inventory estimation technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein, J.E.; Shanahan, K.L.; Baker, R.A.

2015-03-15

Low tritium hydride beds were developed and deployed into tritium service in Savannah River Site. Process beds to be used for low concentration tritium gas were not fitted with instrumentation to perform the steady-state, flowing gas calorimetric inventory measurement method. Low tritium beds contain less than the detection limit of the IBA (In-Bed Accountability) technique used for tritium inventory. This paper describes two techniques for estimating tritium content and uncertainty for low tritium content beds to be used in the facility's physical inventory (PI). PI are performed periodically to assess the quantity of nuclear material used in a facility. Themore » first approach (Mid-point approximation method - MPA) assumes the bed is half-full and uses a gas composition measurement to estimate the tritium inventory and uncertainty. The second approach utilizes the bed's hydride material pressure-composition-temperature (PCT) properties and a gas composition measurement to reduce the uncertainty in the calculated bed inventory.« less

PREFACE: 1st European Conference on Gas Micro Flows (GasMems 2012)

NASA Astrophysics Data System (ADS)

Frijns, Arjan; Valougeorgis, Dimitris; Colin, Stéphane; Baldas, Lucien

2012-05-01

The aim of the 1st European Conference on Gas Micro Flows is to advance research in Europe and worldwide in the field of gas micro flows as well as to improve global fundamental knowledge and to enable technological applications. Gas flows in microsystems are of great importance and touch almost every industrial field (e.g. fluidic microactuators for active control of aerodynamic flows, vacuum generators for extracting biological samples, mass flow and temperature micro-sensors, pressure gauges, micro heat-exchangers for the cooling of electronic components or for chemical applications, and micro gas analyzers or separators). The main characteristic of gas microflows is their rarefaction, which for device design often requires modelling and simulation both by continuous and molecular approaches. In such flows various non-equilibrium transport phenomena appear, while the role played by the interaction between the gas and the solid device surfaces becomes essential. The proposed models of boundary conditions often need an empirical adjustment strongly dependent on the micro manufacturing technique. The 1st European Conference on Gas Micro Flows is organized under the umbrella of the recently established GASMEMS network (www.gasmems.eu/) consisting of 13 participants and six associate members. The main objectives of the network are to structure research and train researchers in the fields of micro gas dynamics, measurement techniques for gaseous flows in micro experimental setups, microstructure design and micro manufacturing with applications in lab and industry. The conference takes place on June 6-8 2012, at the Skiathos Palace Hotel, on the beautiful island of Skiathos, Greece. The conference has received funding from the European Community's Seventh Framework Programme FP7/2007-2013 under grant agreement ITN GASMEMS no. 215504. It owes its success to many people. We would like to acknowledge the support of all members of the Scientific Committee and of all

Sensor Data Qualification Technique Applied to Gas Turbine Engines

NASA Technical Reports Server (NTRS)

Csank, Jeffrey T.; Simon, Donald L.

2013-01-01

This paper applies a previously developed sensor data qualification technique to a commercial aircraft engine simulation known as the Commercial Modular Aero-Propulsion System Simulation 40,000 (C-MAPSS40k). The sensor data qualification technique is designed to detect, isolate, and accommodate faulty sensor measurements. It features sensor networks, which group various sensors together and relies on an empirically derived analytical model to relate the sensor measurements. Relationships between all member sensors of the network are analyzed to detect and isolate any faulty sensor within the network.

Confusing or Ambiguous Upper Gut Symptoms

MedlinePlus

... esophageal sphincter. This is called gastroesophageal reflux – the fundamental abnormality underlying GERD. Unlike vomiting, the regurgitated material ... Belching Bloating and Distension Chronic Pain Medications Self-management Other Management Techniques 8-step Approach to Chronic ...

Investigation Of A Mercury Speciation Technique For Flue Gas Desulfurization Materials

EPA Science Inventory

Most of the synthetic gypsum generated from wet flue gas desulfurization (FGD) scrubbers is currently being used for wallboard production. Because oxidized mercury is readily captured by the wet FGD scrubber, and coal-fired power plants equipped with wet scrubbers desire to bene...

Mobile Measurements of Gas and Particle Emissions from Marcellus Shale Gas Development

NASA Astrophysics Data System (ADS)

DeCarlo, P. F.; Goetz, J. D.; Floerchinger, C. R.; Fortner, E.; Wormhoudt, J.; Knighton, W. B.; Herndon, S.; Kolb, C. E.; Shaw, S. L.; Knipping, E. M.

2013-12-01

Production of natural gas in the Marcellus shale is increasing rapidly due to the vast quantities of natural gas stored in the formation. Transient and long-term activities have associated emissions to the atmosphere of methane, volatile organic compounds, NOx, particulates and other species from gas production and transport infrastructure. In the summer of 2012, a team of researchers from Drexel University and Aerodyne Research deployed the Aerodyne mobile laboratory (AML) and measured in-situ concentrations of gas-phase and aerosol chemical components in the main gas producing regions of Pennsylvania, with the overall goal of understanding the impacts to regional ozone and particulate matter (PM) concentrations. State-of-the-art instruments including quantum cascade laser systems, proton transfer mass spectrometry, tunable diode lasers and a soot particle aerosol mass spectrometer, were used quantify concentrations of pollutants of interest. Chemical species measured include methane, ethane, NO, NO2, CO, CO2, SO2, and many volatile organic compounds, and aerosol size and chemical composition. Tracer-release techniques were employed to link sources with emissions and to quantify emission rates from gas facilities, in order to understand the regional burden of these chemical species from oil and gas development in the Marcellus. Measurements were conducted in two regions of Pennsylvania: the NE region that is predominantly dry gas (95% + methane), and the SW region where wet gas (containing greater than 5% higher hydrocarbons) is found. Regional scale measurements of current levels of air pollutants will be shown and will put into context how further development of the gas resource in one of the largest natural gas fields in the world impacts air quality in a region upwind of the highly urbanized east coast corridor.

Application of gas chromatography to analysis of spirit-based alcoholic beverages.

PubMed

Wiśniewska, Paulina; Śliwińska, Magdalena; Dymerski, Tomasz; Wardencki, Waldemar; Namieśnik, Jacek

2015-01-01

Spirit-based beverages are alcoholic drinks; their production processes are dependent on the type and origin of raw materials. The composition of this complex matrix is difficult to analyze, and scientists commonly choose gas chromatography techniques for this reason. With a wide selection of extraction methods and detectors it is possible to provide qualitative and quantitative analysis for many chemical compounds with various functional groups. This article describes different types of gas chromatography techniques and their most commonly used associated extraction techniques (e.g., LLE, SPME, SPE, SFE, and SBME) and detectors (MS, TOFMS, FID, ECD, NPD, AED, O or EPD). Additionally, brief characteristics of internationally popular spirit-based beverages and application of gas chromatography to the analysis of selected alcoholic drinks are presented.

Finding and Producing Oil and Gas

ERIC Educational Resources Information Center

Geotimes, 1974

1974-01-01

Condenses the current research in exploration for gas and oil as described at a symposium at Case Western Reserve University. Briefly discusses reserves, oil exploration and extraction techniques. (BR)

Evaluation of optimum roughage to concentrate ratio in maize stover based complete rations for efficient microbial biomass production using in vitro gas production technique.

PubMed

Reddy, Y Ramana; Kumari, N Nalini; Monika, T; Sridhar, K

2016-06-01

A study was undertaken to evaluate the optimum roughage to concentrate ratio in maize stover (MS) based complete diets for efficient microbial biomass production (EMBP) using in vitro gas production technique. MS based complete diets with roughage to concentrate ratio of 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, and 30:70 were formulated, and 200 mg of oven-dried sample was incubated in water bath at 39°C along with media (rumen liquor [RL] - buffer) in in vitro gas syringes to evaluate the gas production. The gas produced was recorded at 8 and 24 h of incubation. In vitro organic matter digestibility (IVOMD), metabolizable energy (ME), truly digestible organic matter (TDOM), partitioning factor (PF), and EMBP were calculated using appropriate formulae. Ammonia nitrogen and total volatile fatty acids (TVFAs) production were analyzed in RL fluid-media mixture after 24 h of incubation. In vitro gas production (ml) at 24 h incubation, IVOMD, ME, TDOM, TVFA concentration, and ammonia nitrogen production were increased (p<0.01) in proportion to the increase in the level of concentrate in the diet. Significantly (p<0.01) higher PF and EMBP was noticed in total mixed ration with roughage to concentrate ratio of 60:40 and 50:50 followed by 70:30 and 40:60. Based on the results, it was concluded that the MS can be included in complete rations for ruminants at the level of 50-60% for better microbial biomass synthesis which in turn influences the performance of growing sheep.

Fission gas bubble identification using MATLAB's image processing toolbox

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collette, R.

Automated image processing routines have the potential to aid in the fuel performance evaluation process by eliminating bias in human judgment that may vary from person-to-person or sample-to-sample. This study presents several MATLAB based image analysis routines designed for fission gas void identification in post-irradiation examination of uranium molybdenum (U–Mo) monolithic-type plate fuels. Frequency domain filtration, enlisted as a pre-processing technique, can eliminate artifacts from the image without compromising the critical features of interest. This process is coupled with a bilateral filter, an edge-preserving noise removal technique aimed at preparing the image for optimal segmentation. Adaptive thresholding proved to bemore » the most consistent gray-level feature segmentation technique for U–Mo fuel microstructures. The Sauvola adaptive threshold technique segments the image based on histogram weighting factors in stable contrast regions and local statistics in variable contrast regions. Once all processing is complete, the algorithm outputs the total fission gas void count, the mean void size, and the average porosity. The final results demonstrate an ability to extract fission gas void morphological data faster, more consistently, and at least as accurately as manual segmentation methods. - Highlights: •Automated image processing can aid in the fuel qualification process. •Routines are developed to characterize fission gas bubbles in irradiated U–Mo fuel. •Frequency domain filtration effectively eliminates FIB curtaining artifacts. •Adaptive thresholding proved to be the most accurate segmentation method. •The techniques established are ready to be applied to large scale data extraction testing.« less

Hall effect spintronics for gas detection

NASA Astrophysics Data System (ADS)

Gerber, A.; Kopnov, G.; Karpovski, M.

2017-10-01

We present the concept of magnetic gas detection by the extraordinary Hall effect. The technique is compatible with the existing conductometric gas detection technologies and allows the simultaneous measurement of two independent parameters: resistivity and magnetization affected by the target gas. Feasibility of the approach is demonstrated by detecting low concentration hydrogen using thin CoPd films as the sensor material. The Hall effect sensitivity of the optimized samples exceeds 240% per 104 ppm at hydrogen concentrations below 0.5% in the hydrogen/nitrogen atmosphere, which is more than two orders of magnitude higher than the sensitivity of the conductance detection.

Detection of bacterial growth by gas absorption.

PubMed

Waters, J R

1992-05-01

When 24 different aerobic organisms were grown in a shaken culture, all were found to first absorb gas from the headspace. In a rudimentary medium, such as tryptic soy broth, 16 of the 24 organisms did not produce gas following the initial gas absorption. We have developed a simple, noninvasive method for detecting both gas absorption and production in multiple culture vials. The time to positivity was compared with that obtained by the BACTEC 460 blood culture system. For nearly all of these organisms, there was no difference. For some of those organisms that did not produce gas, e.g. Staphylococcus epidermidis, Moraxella osloensis, and Neisseria meningitidis, detection by gas absorption was a few hours faster. Gas absorption appears to be a promising technique for a new automated blood culture system because of its simplicity and because medium without special additives can be used to detect organisms that do not produce gas.

Microbial deterioration of vacuum-packaged chilled beef cuts and techniques for microbiota detection and characterization: a review.

PubMed

Hernández-Macedo, Maria Lucila; Barancelli, Giovana Verginia; Contreras-Castillo, Carmen Josefina

2011-01-01

Gas production from microbial deterioration in vacuum-packs of chilled meat leads to pack distension, which is commonly referred as blown pack. This phenomenon is attributed to some psychrophilic and psychrotrophic Clostridium species, as well as Enterobacteria. The ability of these microorganisms to grow at refrigeration temperatures makes the control by the meat industry a challenge. This type of deterioration has been reported in many countries including some plants in the Midwestern and Southeastern regions of Brazil. In addition to causing economic losses, spoilage negatively impacts the commercial product brand, thereby impairing the meat industry. In the case of strict anaerobes species they are difficult to grow and isolate using culture methods in conventional microbiology laboratories. Furthermore, conventional culture methods are sometimes not capable of distinguishing species or genera. DNA-based molecular methods are alternative strategies for detecting viable and non-cultivable microorganisms and strict anaerobic microorganisms that are difficult to cultivate. Here, we review the microorganisms and mechanisms involved in the deterioration of vacuum-packaged chilled meat and address the use of molecular methods for detecting specific strict anaerobic microorganisms and microbial communities in meat samples.

On-Board Hydrogen Gas Production System For Stirling Engines

DOEpatents

Johansson, Lennart N.

2004-06-29

A hydrogen production system for use in connection with Stirling engines. The production system generates hydrogen working gas and periodically supplies it to the Stirling engine as its working fluid in instances where loss of such working fluid occurs through usage through operation of the associated Stirling engine. The hydrogen gas may be generated by various techniques including electrolysis and stored by various means including the use of a metal hydride absorbing material. By controlling the temperature of the absorbing material, the stored hydrogen gas may be provided to the Stirling engine as needed. A hydrogen production system for use in connection with Stirling engines. The production system generates hydrogen working gas and periodically supplies it to the Stirling engine as its working fluid in instances where loss of such working fluid occurs through usage through operation of the associated Stirling engine. The hydrogen gas may be generated by various techniques including electrolysis and stored by various means including the use of a metal hydride absorbing material. By controlling the temperature of the absorbing material, the stored hydrogen gas may be provided to the Stirling engine as needed.

Active cleaning technique device

NASA Technical Reports Server (NTRS)

Shannon, R. L.; Gillette, R. B.

1973-01-01

The objective of this program was to develop a laboratory demonstration model of an active cleaning technique (ACT) device. The principle of this device is based primarily on the technique for removing contaminants from optical surfaces. This active cleaning technique involves exposing contaminated surfaces to a plasma containing atomic oxygen or combinations of other reactive gases. The ACT device laboratory demonstration model incorporates, in addition to plasma cleaning, the means to operate the device as an ion source for sputtering experiments. The overall ACT device includes a plasma generation tube, an ion accelerator, a gas supply system, a RF power supply and a high voltage dc power supply.

Some recent developments in headspace gas chromatography

Treesearch

J.Y. Zhu; X.-S. Chai

2005-01-01

In this study, recent developments in headspace gas chromatography (HSGC) are briefly reviewed. Several novel HSGC techniques developed recently are presented in detail. These techniques were developed using the unique characteristics of the headspace sampling process implemented in commercial HSGC systems and therefore can be easily applied in laboratory and...

Nuclear Technology. Course 28: Welding Inspection. Module 28-3, Tungsten Inert Gas (TIG), Metal Inert Gas (MIG) and Submerged Arc Welding.

ERIC Educational Resources Information Center

Espy, John

This third in a series of ten modules for a course titled Welding Inspection presents the apparatus, process techniques, procedures, applications, associated defects, and inspection for the tungsten inert gas, metal inert gas, and submerged arc welding processes. The module follows a typical format that includes the following sections: (1)…

Experimental Study and Numerical Modeling of Gas Flow in Microchannels and Micronozzles

DTIC Science & Technology

2005-12-01

built and used to study gas flows in microscale. Gas velocity measurements in microscale were conducted using both Laser Induced Fluorescence...velocity measurements in microscale were conducted using both Laser Induced Fluorescence technique (LIF) in conjunction with Image Correlation...micronozzles, several velocity measurement techniques have been used, such as laser doppler anemometry (LDA), particle image velocimetry (PIV), molecular

Gas Shielding Technology for Welding and Brazing

NASA Technical Reports Server (NTRS)

Nunes, Arthur J.; Gradl, Paul R.

2012-01-01

Welding is a common method that allows two metallic materials to be joined together with high structural integrity. When joints need to be leak-tight, light-weight, or free of contaminant-trapping seams or surface asperities, welding tends to be specified. There are many welding techniques, each with its own advantages and disadvantages. Some of these techniques include Forge Welding, Gas Tungsten Arc Welding, Friction Stir Welding, and Laser Beam Welding to name a few. Whichever technique is used, the objective is a structural joint that meets the requirements of a particular component or assembly. A key practice in producing quality welds is the use of shielding gas. This article discusses various weld techniques, quality of the welds, and importance of shielding gas in each of those techniques. Metallic bonds, or joints, are produced when metals are put into intimate contact. In the solid-state "blacksmith welding" process, now called Forge Welding (FOW), the site to be joined is pounded into intimate contact. The surfaces to be joined usually need to be heated to make it easier to deform the metal. The surfaces are sprinkled with a flux to melt surface oxides and given a concave shape so that surface contamination can be squeezed out of the joint as the surfaces are pounded together; otherwise the surface contamination would be trapped in the joint and would weaken the weld. In solid-state welding processes surface oxides or other contamination are typically squeezed out of the joint in "flash."

Passive gas separator and accumulator device

DOEpatents

Choe, Hwang; Fallas, Thomas T.

1994-01-01

A separation device employing a gas separation filter and swirler vanes for separating gas from a gasliquid mixture is provided. The cylindrical filter utilizes the principle that surface tension in the pores of the filter prevents gas bubbles from passing through. As a result, the gas collects in the interior region of the filter and coalesces to form larger bubbles in the center of the device. The device is particularly suited for use in microgravity conditions since the swirlers induce a centrifugal force which causes liquid to move from the inner region of the filter, pass the pores, and flow through the outlet of the device while the entrained gas is trapped by the filter. The device includes a cylindrical gas storage screen which is enclosed by the cylindrical gas separation filter. The screen has pores that are larger than those of the filters. The screen prevents larger bubbles that have been formed from reaching and interfering with the pores of the gas separation filter. The device is initially filled with a gas other than that which is to be separated. This technique results in separation of the gas even before gas bubbles are present in the mixture. Initially filling the device with the dissimilar gas and preventing the gas from escaping before operation can be accomplished by sealing the dissimilar gas in the inner region of the separation device with a ruptured disc which can be ruptured when the device is activated for use.

A simplified method for determining heat of combustion of natural gas

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Chegini, Hoshang; Mall, Gerald H.

1987-01-01

A simplified technique for determination of the heat of combustion of natural gas has been developed. It is a variation of the previously developed technique wherein the carrier air, in which the test sample was burnt, was oxygen enriched to adjust the mole fraction of oxygen in the combustion product gases up to that in the carrier air. The new technique eliminates the need for oxygen enrichment of the experimental mixtures and natural gas samples and has been found to predict their heats of combustion to an uncertainty of the order of 1 percent.

Techniques for Reaeration of Hydropower Releases.

DTIC Science & Technology

1983-02-01

peak production from air induction through the baffle ring. The other aeration technique at Norris required modifications to the vacuum-breaker system...of Gas Tracers for Reaeration," Jour. Environ. Div., Proc. Amer. Soc. Civil Engr., 104, 215, April. Rathbun, R. E., 1979, "Estimating the Gas and Dye ...or dissolved in the water, and--last but not least--by the decomposition of bottom mud and by oxidation of the decomposition products stirred up out

Technique of estimation of actual strength of a gas pipeline section at its deformation in landslide action zone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tcherni, V.P.

1996-12-31

The technique is given which permits determination of stress and strain state (SSS) and estimation of actual strength of a section of a buried main gas pipeline (GP) in the case of its deformation in a landslide action zone. The technique is based on the use of three-dimensional coordinates of axial points of the deformed GP section. These coordinates are received by a full-scale survey. The deformed axis of the surveyed GP section is described by the polynomial. The unknown coefficients of the polynomial can be determined from the boundary conditions at points of connection with contiguous undeformed sections asmore » well as by use of minimization methods in mathematical processing of full-scale survey results. The resulting form of GP section`s axis allows one to determine curvatures and, accordingly, bending moments along all the length of the considered section. The influence of soil resistance to longitudinal displacements of a pipeline is used to determine longitudinal forces. Resulting values of bending moments and axial forces as well as the known value of internal pressure are used to analyze all necessary components of an actual SSS of pipeline section and to estimate its strength by elastic analysis.« less

Turbine Engine Flowpath Averaging Techniques

DTIC Science & Technology

1980-10-01

u~%x AEDC- TMR- 8 I-G 1 • R. P TURBINE ENGINE FLOWPATH AVERAGING TECHNIQUES T. W. Skiles ARO, Inc. October 1980 Final Report for Period...COVERED 00-01-1980 to 00-10-1980 4. TITLE AND SUBTITLE Turbine Engine Flowpath Averaging Techniques 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...property for gas turbine engines were investigated. The investigation consisted of a literature review and review of turbine engine current flowpath

Ambient air contamination: Characterization and detection techniques

NASA Technical Reports Server (NTRS)

Nulton, C. P.; Silvus, H. S.

1985-01-01

Techniques to characterize and detect sources of ambient air contamination are described. Chemical techniques to identify indoor contaminants are outlined, they include gas chromatography, or colorimetric detection. Organics generated from indoor materials at ambient conditions and upon combustion are characterized. Piezoelectric quartz crystals are used as precision frequency determining elements in electronic oscillators.

High resolution gas volume change sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dirckx, Joris J. J.; Aernouts, Jef E. F.; Aerts, Johan R. M.

2007-05-15

Changes of gas quantity in a system can be measured either by measuring pressure changes or by measuring volume changes. As sensitive pressure sensors are readily available, pressure change is the commonly used technique. In many physiologic systems, however, buildup of pressure influences the gas exchange mechanisms, thus changing the gas quantity change rate. If one wants to study the gas flow in or out of a biological gas pocket, measurements need to be done at constant pressure. In this article we present a highly sensitive sensor for quantitative measurements of gas volume change at constant pressure. The sensor ismore » based on optical detection of the movement of a droplet of fluid enclosed in a capillary. The device is easy to use and delivers gas volume data at a rate of more than 15 measurements/s and a resolution better than 0.06 {mu}l. At the onset of a gas quantity change the sensor shows a small pressure artifact of less than 15 Pa, and at constant change rates the pressure artifact is smaller than 10 Pa or 0.01% of ambient pressure.« less

Response-time enhancement of a clinical gas analyzer facilitates measurement of breath-by-breath gas exchange.

PubMed

Farmery, A D; Hahn, C E

2000-08-01

Tidal ventilation gas-exchange models in respiratory physiology and medicine not only require solution of mass balance equations breath-by-breath but also may require within-breath measurements, which are instantaneous functions of time. This demands a degree of temporal resolution and fidelity of integration of gas flow and concentration signals that cannot be provided by most clinical gas analyzers because of their slow response times. We have characterized the step responses of the Datex Ultima (Datex Instrumentation, Helsinki, Finland) gas analyzer to oxygen, carbon dioxide, and nitrous oxide in terms of a Gompertz four-parameter sigmoidal function. By inversion of this function, we were able to reduce the rise times for all these gases almost fivefold, and, by its application to real on-line respiratory gas signals, it is possible to achieve a performance comparable to the fastest mass spectrometers. With the use of this technique, measurements required for non-steady-state and tidal gas-exchange models can be made easily and reliably in the clinical setting.

Under the Yoke: Europe’s Natural Gas Dependency on Russia

DTIC Science & Technology

2012-03-01

extraction technique known as hydraulic fracturing or " fracking ". North America’s use of this technique is already increasing availability and... fracking go beyond poisoned water supplies and earthquakes," Earth Times, March 22, 2011, http://www.earthtimes.org/energy/dangers- hydraulic ...nuclear power, the EU’s need for gas is increasing while its limited organic gas sources, such as the North Sea, are depleting. Hydraulic fracturing is

Passive gas separator and accumulator device

DOEpatents

Choe, H.; Fallas, T.T.

1994-08-02

A separation device employing a gas separation filter and swirler vanes for separating gas from a gas-liquid mixture is provided. The cylindrical filter utilizes the principle that surface tension in the pores of the filter prevents gas bubbles from passing through. As a result, the gas collects in the interior region of the filter and coalesces to form larger bubbles in the center of the device. The device is particularly suited for use in microgravity conditions since the swirlers induce a centrifugal force which causes liquid to move from the inner region of the filter, pass the pores, and flow through the outlet of the device while the entrained gas is trapped by the filter. The device includes a cylindrical gas storage screen which is enclosed by the cylindrical gas separation filter. The screen has pores that are larger than those of the filters. The screen prevents larger bubbles that have been formed from reaching and interfering with the pores of the gas separation filter. The device is initially filled with a gas other than that which is to be separated. This technique results in separation of the gas even before gas bubbles are present in the mixture. Initially filling the device with the dissimilar gas and preventing the gas from escaping before operation can be accomplished by sealing the dissimilar gas in the inner region of the separation device with a ruptured disc which can be ruptured when the device is activated for use. 3 figs.

Fuel Injector Patternation Evaluation in Advanced Liquid-Fueled, High Pressure, Gas Turbine Combustors, Using Nonintrusive Optical Diagnostic Techniques

NASA Technical Reports Server (NTRS)

Locke, R. J.; Hicks, Y. R.; Anderson, R. C.; Zaller, M. M.

1998-01-01

Planar laser-induced fluorescence (PLIF) imaging and planar Mie scattering are used to examine the fuel distribution pattern (patternation) for advanced fuel injector concepts in kerosene burning, high pressure gas turbine combustors. Three diverse fuel injector concepts for aerospace applications were investigated under a broad range of operating conditions. Fuel PLIF patternation results are contrasted with those obtained by planar Mie scattering. Further comparison is also made for one injector with data obtained through phase Doppler measurements. Differences in spray patterns for diverse conditions and fuel injector configurations are readily discernible. An examination of the data has shown that a direct determination of the fuel spray angle at realistic conditions is also possible. The results obtained in this study demonstrate the applicability and usefulness of these nonintrusive optical techniques for investigating fuel spray patternation under actual combustor conditions.

Conversion of laser energy to gas kinetic energy

NASA Technical Reports Server (NTRS)

Caledonia, G. E.

1975-01-01

Techniques for the gas phase absorption of laser radiation for conversion to gas kinetic energy are discussed. Absorption by inverse Bremsstrahlung, in which laser energy is converted at a gas kinetic rate in a spectrally continuous process, is briefly described, and absorption by molecular vibrational rotation bands is discussed at length. High pressure absorption is proposed as a means of minimizing gas bleaching and dissociation, the major disadvantages of the molecular absorption process. A band model is presented for predicting the molecular absorption spectra in the high pressure absorption region and is applied to the CO molecule. Use of a rare gas seeded with Fe(CO)5 for converting vibrational modes to translation modes is described.

Digestive and respiratory tract motor responses associated with eructation

PubMed Central

Medda, Bidyut K.; Shaker, Reza

2013-01-01

We studied the digestive and respiratory tract motor responses in 10 chronically instrumented dogs during eructation activated after feeding. Muscles were recorded from the cervical area, thorax, and abdomen. The striated muscles were recorded using EMG and the smooth muscles using strain gauges. We found eructation in three distinct functional phases that were composed of different sets of motor responses: gas escape, barrier elimination, and gas transport. The gas escape phase, activated by gastric distension, consists of relaxation of the lower esophageal sphincter and diaphragmatic hiatus and contraction of the longitudinal muscle of the thoracic esophagus and rectus abdominis. All these motor events promote gas escape from the stomach. The barrier elimination phase, probably activated by rapid gas distension of the thoracic esophagus, consists of relaxation of the pharyngeal constrictors and excitation of dorsal and ventral upper esophageal sphincter distracting muscles, as well as rapid contraction of the diaphragmatic dome fibers. These motor events allow esophagopharyngeal air movement by promoting retrograde airflow and opening of the upper esophageal sphincter. The transport phase, possibly activated secondary to diaphragmatic contraction, consists of a retrograde contraction of the striated muscle esophagus that transports the air from the thoracic esophagus to the pharynx. We hypothesize that the esophageal reverse peristalsis is mediated by elementary reflexes, rather than a coordinated peristaltic response like secondary peristalsis. The phases of eructation can be activated independently of one another or in a different manner to participate in physiological events other than eructation that cause gastroesophageal or esophagogastric reflux. PMID:23578784

Environmental Monitoring and the Gas Industry: Program Manager Handbook

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gregory D. Gillispie

1997-12-01

This document has been developed for the nontechnical gas industry manager who has the responsibility for the development of waste or potentially contaminated soil and groundwater data or must make decisions based on such data for the management or remediation of these materials. It explores the pse of common analytical chemistry instrumentation and associated techniques for identification of environmentally hazardous materials. Sufficient detail is given to familiarize the nontechnical reader with the principles behind the operation of each technique. The scope and realm of the techniques and their constituent variations are portrayed through a discussion of crucial details and, wheremore » appropriate, the depiction of real-life data. It is the author's intention to provide an easily understood handbook for gas industry management. Techniques which determine the presence, composition, and quantification of gas industry wastes are discussed. Greater focus is given to traditional techniques which have been the mainstay of modem analytical benchwork. However, with the continual advancement of instrumental principles and design, several techniques have been included which are likely to receive greater attention in fiture considerations for waste-related detection. Definitions and concepts inherent to a thorough understanding of the principles common to analytical chemistry are discussed. It is also crucial that gas industry managers understand the effects of the various actions which take place before, during, and after the actual sampling step. When a series of sample collection, storage, and transport activities occur, new or inexperienced project managers may overlook or misunderstand the importance of the sequence. Each step has an impact on the final results of the measurement process; errors in judgment or decision making can be costly. Specific techniques and methodologies for the collection, storage, and transport of environmental media samples are not

Measurement techniques investigated for detection of hydrogen chloride gas in ambient air

NASA Technical Reports Server (NTRS)

Gregory, G. L.

1976-01-01

Nine basic techniques are discussed, ranging from concentration (parts per million) to dosage only (parts per million-seconds) measurement techniques. Data for each technique include lower detection limit, response time, instrument status, and in some cases, specificity. Several techniques discussed can detect ambient hydrogen chloride concentrations below 1 part per million with a response time of seconds.

Determination of lysine content based on an in situ pretreatment and headspace gas chromatographic measurement technique.

PubMed

Wan, Xiao-Fang; Liu, Bao-Lian; Yu, Teng; Yan, Ning; Chai, Xin-Sheng; Li, You-Ming; Chen, Guang-Xue

2018-05-01

This work reports on a simple method for the determination of lysine content by an in situ sample pretreatment and headspace gas chromatographic measurement (HS-GC) technique, based on carbon dioxide (CO 2 ) formation from the pretreatment reaction (between lysine and ninhydrin solution) in a closed vial. It was observed that complete lysine conversion to CO 2 could be achieved within 60 min at 60 °C in a phosphate buffer medium (pH = 4.0), with a minimum molar ratio of ninhydrin/lysine of 16. The results showed that the method had a good precision (RSD < 5.23%) and accuracy (within 6.80%), compared to the results measured by a reference method (ninhydrin spectroscopic method). Due to the feature of in situ sample pretreatment and headspace measurement, the present method becomes very simple and particularly suitable to be used for batch sample analysis in lysine-related research and applications. Graphical abstract The flow path of the reaction and HS-GC measurement for the lysine analysis.

Elucidating Environmental Fingerprinting Mechanisms of Unconventional Gas Development through Hydrocarbon Analysis.

PubMed

Piotrowski, Paulina K; Weggler, Benedikt A; Yoxtheimer, David A; Kelly, Christina N; Barth-Naftilan, Erica; Saiers, James E; Dorman, Frank L

2018-04-17

Hydraulic fracturing is an increasingly common technique for the extraction of natural gas entrapped in shale formations. This technique has been highly criticized due to the possibility of environmental contamination, underscoring the need for method development to identify chemical factors that could be utilized in point-source identification of environmental contamination events. Here, we utilize comprehensive two-dimensional gas chromatography (GC × GC) coupled to high-resolution time-of-flight (HRT) mass spectrometry, which offers a unique instrumental combination allowing for petroleomics hydrocarbon fingerprinting. Four flowback fluids from Marcellus shale gas wells in geographic proximity were analyzed for differentiating factors that could be exploited in environmental forensics investigations of shale gas impacts. Kendrick mass defect (KMD) plots of these flowback fluids illustrated well-to-well differences in heteroatomic substituted hydrocarbons, while GC × GC separations showed variance in cyclic hydrocarbons and polyaromatic hydrocarbons among the four wells. Additionally, generating plots that combine GC × GC separation with KMD established a novel data-rich visualization technique that further differentiated the samples.

Intra- and Inter-observer Variability of Measurements of the Laxity Index on Stress Radiographs Performed with the Vezzoni-Modified Badertscher Hip Distension Device.

PubMed

Bertal, Mileva; Vezzoni, Aldo; Houdellier, Blandine; Bogaerts, Evelien; Stock, Emmelie; Polis, Ingeborgh; Deforce, Dieter; Saunders, Jimmy H; Broeckx, Bart J G

2018-06-02

 To describe and evaluate the accuracy, intra- and inter-observer variability of the laxity index (LI), used to quantify hip laxity on stress radiographs obtained with the Vezzoni-modified Badertscher distension device (VMBDD).  Stress radiographs of 10 dogs obtained with the VMBDD were measured three times by an experienced observer. Six participants with different backgrounds (two ECVDI residents, two PhD students, two veterinary assistants) followed a short presentation and performed subsequently the measurements four times in two separate sessions. The effect of self-learning, feedback and specialization on the accuracy of the measurements was assessed.  While the intra- and inter-observer variability were in agreement with other studies, the results of the experienced observer indicated that the variability can be very low. Neither feedback nor self-learning improved the results. A high degree of experience in radiographic assessment was not necessary to perform the measurements correctly.  As the LI measurements were acceptable after a short presentation, they support the use of VMBDD for a complete and correct in-house evaluation of the hip joint by trained clinicians. However, we propose that, in the context of screening, measurements should be performed by a limited number of experienced examiners, to limit the impact of the inter-observer variability. Schattauer GmbH Stuttgart.

Gas hydrate hunting in China seas

NASA Astrophysics Data System (ADS)

Yang, J.; Zhang, X.; Chen, J.; Xiang, Q.; Ye, Y.; Gong, J.

2003-04-01

Gas hydrate research is a hotspot now in geosciences. Many countries have carried on gas hydrate survey and research for many years. China, as a country with large sea areas unfolded gas hydrate research work in its marine areas in 1999 and tries to keep pace with the advanced countries on gas hydrate study. Substantial funds were launched by various governmental and non-governmental funding agencies to support gas hydrate research. Many institutions on marine geosciences are involved in. China Geological Survey (CGS) has launched several research projects in the sea. So far, some fieldwork such as seismic survey, sampling, profiling, underwater video imaging have been done in South China Sea and East China Sea areas. Some preliminary results have been achieved. BSRs are found in many seismic profiles. Some potential gas hydrate bearing areas are marked and potential amount of gas hydrate resources is calculated. At the same time, gas hydrate laboratory was founded and successful experiments have been carried out to model the gas hydrate synthesis in accordance with the geological condition of the China seas. Now, gas hydrate detecting techniques such as sampling equipment (PCS), seismic data processing, interpretation and the formation mechanism study as well as environmental effect research are undergoing. Though China's gas hydrate research work is still at its initial stage, China is willing to be an active member in the international society of gas hydrate study and hopes to contribute its effort.

Laser Calorimetry Spectroscopy for ppm-level Dissolved Gas Detection and Analysis

PubMed Central

K. S., Nagapriya; Sinha, Shashank; R., Prashanth; Poonacha, Samhitha; Chaudhry, Gunaranjan; Bhattacharya, Anandaroop; Choudhury, Niloy; Mahalik, Saroj; Maity, Sandip

2017-01-01

In this paper we report a newly developed technique – laser calorimetry spectroscopy (LCS), which is a combination of laser absorption spectroscopy and calorimetry - for the detection of gases dissolved in liquids. The technique involves determination of concentration of a dissolved gas by irradiating the liquid with light of a wavelength where the gas absorbs, and measuring the temperature change caused by the absorbance. Conventionally, detection of dissolved gases with sufficient sensitivity and specificity was done by first extracting the gases from the liquid and then analyzing the gases using techniques such as gas chromatography. Using LCS, we have been able to detect ppm levels of dissolved gases without extracting them from the liquid. In this paper, we show the detection of dissolved acetylene in transformer oil in the mid infrared (MIR) wavelength (3021 nm) region. PMID:28218304

Laser Calorimetry Spectroscopy for ppm-level Dissolved Gas Detection and Analysis.

PubMed

K S, Nagapriya; Sinha, Shashank; R, Prashanth; Poonacha, Samhitha; Chaudhry, Gunaranjan; Bhattacharya, Anandaroop; Choudhury, Niloy; Mahalik, Saroj; Maity, Sandip

2017-02-20

In this paper we report a newly developed technique - laser calorimetry spectroscopy (LCS), which is a combination of laser absorption spectroscopy and calorimetry - for the detection of gases dissolved in liquids. The technique involves determination of concentration of a dissolved gas by irradiating the liquid with light of a wavelength where the gas absorbs, and measuring the temperature change caused by the absorbance. Conventionally, detection of dissolved gases with sufficient sensitivity and specificity was done by first extracting the gases from the liquid and then analyzing the gases using techniques such as gas chromatography. Using LCS, we have been able to detect ppm levels of dissolved gases without extracting them from the liquid. In this paper, we show the detection of dissolved acetylene in transformer oil in the mid infrared (MIR) wavelength (3021 nm) region.

A novel visually CO2 controlled alveolar breath sampling technique.

PubMed

Birken, Thomas; Schubert, Jochen; Miekisch, Wolfram; Nöldge-Schomburg, Gabriele

2006-01-01

A crucial issue in the analysis of exhaled breath is the collection of gaseous samples. The analysis of pure alveolar gas is the method of choice if contamination of samples is to be minimized. Monitoring of expired CO2 can be used to identify alveolar gas. The purpose of this study was to evaluate a bed side version of this technique using visual CO2 control by means of a capnometer. 22 mechanically ventilated patients of an ICU were enrolled into the study. Alveolar and mixed expiratory gas, and arterial blood were sampled. PCO2 in blood and gas was determined in a blood gas analyzer. End tidal PCO2 was monitored in all patients by a fast responding main stream capnometry. Taking the gaseous samples was visually synchronized with the expired CO2. Alveolar CO2 contents measured during two different respiratory cycles were identical (p 0.86). The variation of the CO2 content during 10 measurements in one patient was lower than 4%. Arterial PCO2, PCO2 in alveolar gas and end tidal PCO2 showed positive correlation. The visually CO2-controlled sampling technique of alveolar gas is a reliable and reproducible method. It represents an important step in simplifying and standardizing breath analysis.

High-Resolution Gas Metering and Nonintrusive Appliance Load Monitoring System

NASA Astrophysics Data System (ADS)

Tewolde, Mahder

This thesis deals with design and implementation of a high-resolution metering system for residential natural gas meters. Detailed experimental measurements are performed on the meter to characterize and understand its measurement properties. Results from these experiments are used to develop a simple, fast and accurate technique to non-intrusively monitor the gas consumption of individual appliances in homes by resolving small amounts of gas usage. The technique is applied on an existing meter retrofitted with a module that includes a high-resolution encoder to collect gas flow data and a microprocessor to analyze and identify appliance load profiles. This approach provides a number of appealing features including low cost, easy installation and integration with automated meter reading (AMR) systems. The application of this method to residential gas meters currently deployed is also given. This is done by performing a load simulation on realistic gas loads with the aim of identifying the necessary parameters that minimize the cost and complexity of the mechanical encoder module. The primary benefits of the system are efficiency analysis, appliance health monitoring and real-time customer feedback of gas usage. Additional benefits of include the ability to detect very small leaks and theft. This system has the potential for wide scale market adoption.

Geophysical assessments of renewable gas energy compressed in geologic pore storage reservoirs.

PubMed

Al Hagrey, Said Attia; Köhn, Daniel; Rabbel, Wolfgang

2014-01-01

Renewable energy resources can indisputably minimize the threat of global warming and climate change. However, they are intermittent and need buffer storage to bridge the time-gap between production (off peak) and demand peaks. Based on geologic and geochemical reasons, the North German Basin has a very large capacity for compressed air/gas energy storage CAES in porous saltwater aquifers and salt cavities. Replacing pore reservoir brine with CAES causes changes in physical properties (elastic moduli, density and electrical properties) and justify applications of integrative geophysical methods for monitoring this energy storage. Here we apply techniques of the elastic full waveform inversion FWI, electric resistivity tomography ERT and gravity to map and quantify a gradually saturated gas plume injected in a thin deep saline aquifer within the North German Basin. For this subsurface model scenario we generated different synthetic data sets without and with adding random noise in order to robust the applied techniques for the real field applications. Datasets are inverted by posing different constraints on the initial model. Results reveal principally the capability of the applied integrative geophysical approach to resolve the CAES targets (plume, host reservoir, and cap rock). Constrained inversion models of elastic FWI and ERT are even able to recover well the gradual gas desaturation with depth. The spatial parameters accurately recovered from each technique are applied in the adequate petrophysical equations to yield precise quantifications of gas saturations. Resulting models of gas saturations independently determined from elastic FWI and ERT techniques are in accordance with each other and with the input (true) saturation model. Moreover, the gravity technique show high sensitivity to the mass deficit resulting from the gas storage and can resolve saturations and temporal saturation changes down to ±3% after reducing any shallow fluctuation such as that of

Microfabricated packed gas chromatographic column

DOEpatents

Kottenstette, Richard; Matzke, Carolyn M.; Frye-Mason, Gregory C.

2003-12-16

A new class of miniaturized gas chromatographic columns has been invented. These chromatographic columns are formed using conventional micromachining techniques, and allow packed columns having lengths on the order of a meter to be fabricated with a footprint on the order of a square centimeter.

Oil and gas impacts on transportation.

DOT National Transportation Integrated Search

2015-01-01

Colorados oil and gas industry is continually evolving, and there have been considerable changes in drilling techniques and geographic focus since the 2010 CDOT research study on Energy Development and the Transportation System. This research stud...

Measurement of the distribution of ventilation-perfusion ratios in the human lung with proton MRI: comparison with the multiple inert-gas elimination technique.

PubMed

Sá, Rui Carlos; Henderson, A Cortney; Simonson, Tatum; Arai, Tatsuya J; Wagner, Harrieth; Theilmann, Rebecca J; Wagner, Peter D; Prisk, G Kim; Hopkins, Susan R

2017-07-01

We have developed a novel functional proton magnetic resonance imaging (MRI) technique to measure regional ventilation-perfusion (V̇ A /Q̇) ratio in the lung. We conducted a comparison study of this technique in healthy subjects ( n = 7, age = 42 ± 16 yr, Forced expiratory volume in 1 s = 94% predicted), by comparing data measured using MRI to that obtained from the multiple inert gas elimination technique (MIGET). Regional ventilation measured in a sagittal lung slice using Specific Ventilation Imaging was combined with proton density measured using a fast gradient-echo sequence to calculate regional alveolar ventilation, registered with perfusion images acquired using arterial spin labeling, and divided on a voxel-by-voxel basis to obtain regional V̇ A /Q̇ ratio. LogSDV̇ and LogSDQ̇, measures of heterogeneity derived from the standard deviation (log scale) of the ventilation and perfusion vs. V̇ A /Q̇ ratio histograms respectively, were calculated. On a separate day, subjects underwent study with MIGET and LogSDV̇ and LogSDQ̇ were calculated from MIGET data using the 50-compartment model. MIGET LogSDV̇ and LogSDQ̇ were normal in all subjects. LogSDQ̇ was highly correlated between MRI and MIGET (R = 0.89, P = 0.007); the intercept was not significantly different from zero (-0.062, P = 0.65) and the slope did not significantly differ from identity (1.29, P = 0.34). MIGET and MRI measures of LogSDV̇ were well correlated (R = 0.83, P = 0.02); the intercept differed from zero (0.20, P = 0.04) and the slope deviated from the line of identity (0.52, P = 0.01). We conclude that in normal subjects, there is a reasonable agreement between MIGET measures of heterogeneity and those from proton MRI measured in a single slice of lung. NEW & NOTEWORTHY We report a comparison of a new proton MRI technique to measure regional V̇ A /Q̇ ratio against the multiple inert gas elimination technique (MIGET). The study reports good relationships

Applications of Electromigration Techniques: Applications of Electromigration Techniques in Food Analysis

NASA Astrophysics Data System (ADS)

Wieczorek, Piotr; Ligor, Magdalena; Buszewski, Bogusław

Electromigration techniques, including capillary electrophoresis (CE), are widely used for separation and identification of compounds present in food products. These techniques may also be considered as alternate and complementary with respect to commonly used analytical techniques, such as high-performance liquid chromatography (HPLC), or gas chromatography (GC). Applications of CE concern the determination of high-molecular compounds, like polyphenols, including flavonoids, pigments, vitamins, food additives (preservatives, antioxidants, sweeteners, artificial pigments) are presented. Also, the method developed for the determination of proteins and peptides composed of amino acids, which are basic components of food products, are studied. Other substances such as carbohydrates, nucleic acids, biogenic amines, natural toxins, and other contaminations including pesticides and antibiotics are discussed. The possibility of CE application in food control laboratories, where analysis of the composition of food and food products are conducted, is of great importance. CE technique may be used during the control of technological processes in the food industry and for the identification of numerous compounds present in food. Due to the numerous advantages of the CE technique it is successfully used in routine food analysis.

PIV Measurements of Gas Flow Fields from Burning End

NASA Astrophysics Data System (ADS)

Huang, Yifei; Wu, Junzhang; Zeng, Jingsong; Tang, Darong; Du, Liang

2017-12-01

To study the influence of cigarette gas on the environment, it is necessary to know the cigarette gas flow fields from burning end. By using PIV technique, in order to reveal velocity characteristics of gas flow fields, the velocities of cigarette gas flow fields was analyzed with different stepping motor frequencies corresponding to suction pressures, and the trend of velocity has been given with image fitting. The results shows that the velocities of the burning end increased with suction pressures; Between velocities of the burning end and suction pressures, the relations present polynomial rule; The cigarette gas diffusion in combustion process is faster than in the smoldering process.

Measurement techniques for trace metals in coal-plant effluents: A brief review

NASA Technical Reports Server (NTRS)

Singh, J. J.

1979-01-01

The strong features and limitations of techniques for determining trace elements in aerosols emitted from coal plants are discussed. Techniques reviewed include atomic absorption spectroscopy, charged particle scattering and activation, instrumental neutron activation analysis, gas/liquid chromatography, gas chromatographic/mass spectrometric methods, X-ray fluorescence, and charged-particle-induced X-ray emission. The latter two methods are emphasized. They provide simultaneous, sensitive multielement analyses and lend themselves readily to depth profiling. It is recommended that whenever feasible, two or more complementary techniques should be used for analyzing environmental samples.

Environmental risks associated with unconventional gas extraction: an Australian perspective

NASA Astrophysics Data System (ADS)

Mallants, Dirk; Bekele, Elise; Schmidt, Wolfgang; Miotlinski, Konrad; Gerke Gerke, Kirill

2015-04-01

Coal seam gas is naturally occurring methane gas (CH4) formed by the degradation of organic material in coal seam layers over geological times, typically over several millions of years. Unlike conventional gas resources, which occur as discrete accumulations in traps formed by folds and other structures in sedimentary layers, coal seam gas is generally trapped in low permeable rock by adsorption of the gas molecules within the rock formation and cannot migrate to a trap and form a conventional gas deposit. Extraction of coal seam gas requires producers to de pressurise the coal measures by abstracting large amounts of groundwater through pumping. For coal measures that have too low permeabilities for gas extraction to be economical, mechanical and chemical techniques are required to increase permeability and thus gas yield. One such technique is hydraulic fracturing (HF). Hydraulic fracturing increases the rate and total amount of gas extracted from coal seam gas reservoirs. The process of hydraulic fracturing involves injecting large volumes of hydraulic fracturing fluids under high pressure into the coal seam layers to open up (i.e. fracture) the gas-containing coal layers, thus facilitating extraction of methane gas through pumping. After a hydraulic fracturing operation has been completed in a coal seam gas well, the fracturing fluid pressure is lowered and a significant proportion of the injected fluid returns to the surface as "flowback" water via coal seam gas wells. Flowback water is fluid that returns to the surface after hydraulic fracturing has occurred but before the well is put into production; whereas produced water is fluid from the coal measure that is pumped to the surface after the well is in production. This paper summarises available literature data from Australian coal seam gas practices on i) spills from hydraulic fracturing-related fluids used during coal seam gas drilling and hydraulic fracturing operations, ii) leaks to soil and shallow

Fabrication of glass gas cells for the HALOE and MAPS satellite experiments

NASA Technical Reports Server (NTRS)

Sullivan, E. M.; Walthall, H. G.

1984-01-01

The Halogen Occultation Experiment (HALOE) and the Measurement of Air Pollution from Satellites (MAPS) experiment are satellite-borne experiments which measure trace constituents in the Earth's atmosphere. The instruments which obtain the data for these experiments are based on the gas filter correlation radiometer measurement technique. In this technique, small samples of the gases of interest are encapsulated in glass cylinders, called gas cells, which act as very selective optical filters. This report describes the techniques employed in the fabrication of the gas cells for the HALOE and MAPS instruments. Details of the method used to fuse the sapphire windows (required for IR transmission) to the glass cell bodies are presented along with detailed descriptions of the jigs and fixtures used during the assembly process. The techniques and equipment used for window inspection and for pairing the HALOE windows are discussed. Cell body materials and the steps involved in preparing the cell bodies for the glass-to-sapphire fusion process are given.

Fission gas bubble identification using MATLAB's image processing toolbox

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collette, R.; King, J.; Keiser, Jr., D.

Automated image processing routines have the potential to aid in the fuel performance evaluation process by eliminating bias in human judgment that may vary from person-to-person or sample-to-sample. In addition, this study presents several MATLAB based image analysis routines designed for fission gas void identification in post-irradiation examination of uranium molybdenum (U–Mo) monolithic-type plate fuels. Frequency domain filtration, enlisted as a pre-processing technique, can eliminate artifacts from the image without compromising the critical features of interest. This process is coupled with a bilateral filter, an edge-preserving noise removal technique aimed at preparing the image for optimal segmentation. Adaptive thresholding provedmore » to be the most consistent gray-level feature segmentation technique for U–Mo fuel microstructures. The Sauvola adaptive threshold technique segments the image based on histogram weighting factors in stable contrast regions and local statistics in variable contrast regions. Once all processing is complete, the algorithm outputs the total fission gas void count, the mean void size, and the average porosity. The final results demonstrate an ability to extract fission gas void morphological data faster, more consistently, and at least as accurately as manual segmentation methods.« less

Fission gas bubble identification using MATLAB's image processing toolbox

DOE PAGES

Collette, R.; King, J.; Keiser, Jr., D.; ...

2016-06-08

Automated image processing routines have the potential to aid in the fuel performance evaluation process by eliminating bias in human judgment that may vary from person-to-person or sample-to-sample. In addition, this study presents several MATLAB based image analysis routines designed for fission gas void identification in post-irradiation examination of uranium molybdenum (U–Mo) monolithic-type plate fuels. Frequency domain filtration, enlisted as a pre-processing technique, can eliminate artifacts from the image without compromising the critical features of interest. This process is coupled with a bilateral filter, an edge-preserving noise removal technique aimed at preparing the image for optimal segmentation. Adaptive thresholding provedmore » to be the most consistent gray-level feature segmentation technique for U–Mo fuel microstructures. The Sauvola adaptive threshold technique segments the image based on histogram weighting factors in stable contrast regions and local statistics in variable contrast regions. Once all processing is complete, the algorithm outputs the total fission gas void count, the mean void size, and the average porosity. The final results demonstrate an ability to extract fission gas void morphological data faster, more consistently, and at least as accurately as manual segmentation methods.« less

Searching for anomalous methane in shallow groundwater near shale gas wells

NASA Astrophysics Data System (ADS)

Li, Zhenhui; You, Cheng; Gonzales, Matthew; Wendt, Anna K.; Wu, Fei; Brantley, Susan L.

2016-12-01

Since the 1800s, natural gas has been extracted from wells drilled into conventional reservoirs. Today, gas is also extracted from shale using high-volume hydraulic fracturing (HVHF). These wells sometimes leak methane and must be re-sealed with cement. Some researchers argue that methane concentrations, C, increase in groundwater near shale-gas wells and that ;fracked; wells leak more than conventional wells. We developed techniques to mine datasets of groundwater chemistry in Pennsylvania townships where contamination had been reported. Values of C measured in shallow private water wells were discovered to increase with proximity to faults and to conventional, but not shale-gas, wells in the entire area. However, in small subareas, C increased with proximity to some shale-gas wells. Data mining was used to map a few hotspots where C significantly correlates with distance to faults and gas wells. Near the hotspots, 3 out of 132 shale-gas wells ( 2%) and 4 out of 15 conventional wells (27%) intersect faults at depths where they are reported to be uncased or uncemented. These results demonstrate that even though these data techniques do not establish causation, they can elucidate the controls on natural methane emission along faults and may have implications for gas well construction.

Searching for anomalous methane in shallow groundwater near shale gas wells.

PubMed

Li, Zhenhui; You, Cheng; Gonzales, Matthew; Wendt, Anna K; Wu, Fei; Brantley, Susan L

2016-12-01

Since the 1800s, natural gas has been extracted from wells drilled into conventional reservoirs. Today, gas is also extracted from shale using high-volume hydraulic fracturing (HVHF). These wells sometimes leak methane and must be re-sealed with cement. Some researchers argue that methane concentrations, C, increase in groundwater near shale-gas wells and that "fracked" wells leak more than conventional wells. We developed techniques to mine datasets of groundwater chemistry in Pennsylvania townships where contamination had been reported. Values of C measured in shallow private water wells were discovered to increase with proximity to faults and to conventional, but not shale-gas, wells in the entire area. However, in small subareas, C increased with proximity to some shale-gas wells. Data mining was used to map a few hotspots where C significantly correlates with distance to faults and gas wells. Near the hotspots, 3 out of 132 shale-gas wells (~2%) and 4 out of 15 conventional wells (27%) intersect faults at depths where they are reported to be uncased or uncemented. These results demonstrate that even though these data techniques do not establish causation, they can elucidate the controls on natural methane emission along faults and may have implications for gas well construction. Copyright © 2016 Elsevier B.V. All rights reserved.

Improvement in QEPAS system utilizing a second harmonic based wavelength calibration technique

NASA Astrophysics Data System (ADS)

Zhang, Qinduan; Chang, Jun; Wang, Fupeng; Wang, Zongliang; Xie, Yulei; Gong, Weihua

2018-05-01

A simple laser wavelength calibration technique, based on second harmonic signal, is demonstrated in this paper to improve the performance of quartz enhanced photoacoustic spectroscopy (QEPAS) gas sensing system, e.g. improving the signal to noise ratio (SNR), detection limit and long-term stability. Constant current, corresponding to the gas absorption line, combining f/2 frequency sinusoidal signal are used to drive the laser (constant driving mode), a software based real-time wavelength calibration technique is developed to eliminate the wavelength drift due to ambient fluctuations. Compared to conventional wavelength modulation spectroscopy (WMS), this method allows lower filtering bandwidth and averaging algorithm applied to QEPAS system, improving SNR and detection limit. In addition, the real-time wavelength calibration technique guarantees the laser output is modulated steadily at gas absorption line. Water vapor is chosen as an objective gas to evaluate its performance compared to constant driving mode and conventional WMS system. The water vapor sensor was designed insensitive to the incoherent external acoustic noise by the numerical averaging technique. As a result, the SNR increases 12.87 times in wavelength calibration technique based system compared to conventional WMS system. The new system achieved a better linear response (R2 = 0 . 9995) in concentration range from 300 to 2000 ppmv, and achieved a minimum detection limit (MDL) of 630 ppbv.

Upscaling pore pressure-dependent gas permeability in shales

NASA Astrophysics Data System (ADS)

Ghanbarian, Behzad; Javadpour, Farzam

2017-04-01

Upscaling pore pressure dependence of shale gas permeability is of great importance and interest in the investigation of gas production in unconventional reservoirs. In this study, we apply the Effective Medium Approximation, an upscaling technique from statistical physics, and modify the Doyen model for unconventional rocks. We develop an upscaling model to estimate the pore pressure-dependent gas permeability from pore throat size distribution, pore connectivity, tortuosity, porosity, and gas characteristics. We compare our adapted model with six data sets: three experiments, one pore-network model, and two lattice-Boltzmann simulations. Results showed that the proposed model estimated the gas permeability within a factor of 3 of the measurements/simulations in all data sets except the Eagle Ford experiment for which we discuss plausible sources of discrepancies.

Multiple Point Dynamic Gas Density Measurements Using Molecular Rayleigh Scattering

NASA Technical Reports Server (NTRS)

Seasholtz, Richard; Panda, Jayanta

1999-01-01

A nonintrusive technique for measuring dynamic gas density properties is described. Molecular Rayleigh scattering is used to measure the time-history of gas density simultaneously at eight spatial locations at a 50 kHz sampling rate. The data are analyzed using the Welch method of modified periodograms to reduce measurement uncertainty. Cross-correlations, power spectral density functions, cross-spectral density functions, and coherence functions may be obtained from the data. The technique is demonstrated using low speed co-flowing jets with a heated inner jet.

Applications of optical measurement technology in pollution gas monitoring at thermal power plants

NASA Astrophysics Data System (ADS)

Wang, Jian; Yu, Dahai; Ye, Huajun; Yang, Jianhu; Ke, Liang; Han, Shuanglai; Gu, Haitao; Chen, Yingbin

2011-11-01

This paper presents the work of using advanced optical measurement techniques to implement stack gas emission monitoring and process control. A system is designed to conduct online measurement of SO2/NOX and mercury emission from stacks and slipping NH3 of de-nitrification process. The system is consisted of SO2/NOX monitoring subsystem, mercury monitoring subsystem, and NH3 monitoring subsystem. The SO2/NOX monitoring subsystem is developed based on the ultraviolet differential optical absorption spectroscopy (UV-DOAS) technique. By using this technique, a linearity error less than +/-1% F.S. is achieved, and the measurement errors resulting from optical path contamination and light fluctuation are removed. Moreover, this subsystem employs in situ extraction and hot-wet line sampling technique to significantly reduce SO2 loss due to condensation and protect gas pipeline from corrosion. The mercury monitoring subsystem is used to measure the concentration of element mercury (Hg0), oxidized mercury (Hg2+), and total gaseous mercury (HgT) in the flue gas exhaust. The measurement of Hg with a low detection limit (0.1μg/m3) and a high sensitivity is realized by using cold vapor atom fluorescence spectroscopy (CVAFS) technique. This subsystem is also equipped with an inertial separation type sampling technique to prevent gas pipeline from being clogged and to reduce speciation mercury measurement error. The NH3 monitoring subsystem is developed to measure the concentration of slipping NH3 and then to help improving the efficiency of de-nitrification. The NH3 concentration as low as 0.1ppm is able to be measured by using the off-axis integrated cavity output spectroscopy (ICOS) and the tunable diode laser absorption spectroscopy (TDLAS) techniques. The problem of trace NH3 sampling loss is solved by applying heating the gas pipelines when the measurement is running.

Comparison of the radioactive and modified techniques for measurement of stream reaeration coefficients

USGS Publications Warehouse

Rathbun, R.E.; Grant, R. Stephen

1978-01-01

There are advantages and disadvantages to both the radioactive and modified tracer techniques. The main advantage of the radioactive technique is that the tracer gas is chemically inert; the main disadvantage is that a radioactive isotope of the gas must be used to obtain the necessary analytical sensitivity. The main advantage of the modified technique is that radioactive tracers are not necessary; the main disadvantage is that the hydrocarbon tracer gases may be subject to biological degradation and sorption losses. Results of this comparison study suggest that the modified technique is a promising alternative to the use of radioactive tracers.

Detecting gas hydrate behavior in crude oil using NMR.

PubMed

Gao, Shuqiang; House, Waylon; Chapman, Walter G

2006-04-06

Because of the associated experimental difficulties, natural gas hydrate behavior in black oil is poorly understood despite its grave importance in deep-water flow assurance. Since the hydrate cannot be visually observed in black oil, traditional methods often rely on gas pressure changes to monitor hydrate formation and dissociation. Because gases have to diffuse through the liquid phase for hydrate behavior to create pressure responses, the complication of gas mass transfer is involved and hydrate behavior is only indirectly observed. This pressure monitoring technique encounters difficulties when the oil phase is too viscous, the amount of water is too small, or the gas phase is absent. In this work we employ proton nuclear magnetic resonance (NMR) spectroscopy to observe directly the liquid-to-solid conversion of the water component in black oil emulsions. The technique relies on two facts. The first, well-known, is that water becomes essentially invisible to liquid state NMR as it becomes immobile, as in hydrate or ice formation. The second, our recent finding, is that in high magnetic fields of sufficient homogeneity, it is possible to distinguish water from black oil spectrally by their chemical shifts. By following changes in the area of the water peak, the process of hydrate conversion can be measured, and, at lower temperatures, the formation of ice. Taking only seconds to accomplish, this measurement is nearly direct in contrast to conventional techniques that measure the pressure changes of the whole system and assume these changes represent formation or dissociation of hydrates - rather than simply changes in solubility. This new technique clearly can provide accurate hydrate thermodynamic data in black oils. Because the technique measures the total mobile water with rapidity, extensions should prove valuable in studying the dynamics of phase transitions in emulsions.

Gas Classification Using Deep Convolutional Neural Networks.

PubMed

Peng, Pai; Zhao, Xiaojin; Pan, Xiaofang; Ye, Wenbin

2018-01-08

In this work, we propose a novel Deep Convolutional Neural Network (DCNN) tailored for gas classification. Inspired by the great success of DCNN in the field of computer vision, we designed a DCNN with up to 38 layers. In general, the proposed gas neural network, named GasNet, consists of: six convolutional blocks, each block consist of six layers; a pooling layer; and a fully-connected layer. Together, these various layers make up a powerful deep model for gas classification. Experimental results show that the proposed DCNN method is an effective technique for classifying electronic nose data. We also demonstrate that the DCNN method can provide higher classification accuracy than comparable Support Vector Machine (SVM) methods and Multiple Layer Perceptron (MLP).

Gas Classification Using Deep Convolutional Neural Networks

PubMed Central

Peng, Pai; Zhao, Xiaojin; Pan, Xiaofang; Ye, Wenbin

2018-01-01

In this work, we propose a novel Deep Convolutional Neural Network (DCNN) tailored for gas classification. Inspired by the great success of DCNN in the field of computer vision, we designed a DCNN with up to 38 layers. In general, the proposed gas neural network, named GasNet, consists of: six convolutional blocks, each block consist of six layers; a pooling layer; and a fully-connected layer. Together, these various layers make up a powerful deep model for gas classification. Experimental results show that the proposed DCNN method is an effective technique for classifying electronic nose data. We also demonstrate that the DCNN method can provide higher classification accuracy than comparable Support Vector Machine (SVM) methods and Multiple Layer Perceptron (MLP). PMID:29316723

Detonation velocity in poorly mixed gas mixtures

NASA Astrophysics Data System (ADS)

Prokhorov, E. S.

2017-10-01

The technique for computation of the average velocity of plane detonation wave front in poorly mixed mixture of gaseous hydrocarbon fuel and oxygen is proposed. Here it is assumed that along the direction of detonation propagation the chemical composition of the mixture has periodic fluctuations caused, for example, by layered stratification of gas charge. The technique is based on the analysis of functional dependence of ideal (Chapman-Jouget) detonation velocity on mole fraction (with respect to molar concentration) of the fuel. It is shown that the average velocity of detonation can be significantly (by more than 10%) less than the velocity of ideal detonation. The dependence that permits to estimate the degree of mixing of gas mixture basing on the measurements of average detonation velocity is established.

Parallel decrease in arterial distensibility and in endothelium-dependent dilatation in young women with a history of pre-eclampsia.

PubMed

Pàez, Olga; Alfie, José; Gorosito, Marta; Puleio, Pablo; de Maria, Marcelo; Prieto, Noemì; Majul, Claudio

2009-10-01

Pre-eclampsia not only complicates 5 to 8% of pregnancies but also increases the risk of maternal cardiovascular disease and mortality later in life. We analyzed three different aspects of arterial function (pulse wave velocity, augmentation index, and flow-mediated dilatation), in 55 nonpregnant, normotensive women (18-33 years old) according to their gestational history: 15 nulliparous, 20 with a previous normotensive, and 20 formerly pre-eclamptic pregnancy. Former pre-eclamptic women showed a significantly higher augmentation index and pulse wave velocity (P < 0.001 and P < 0.05, respectively) and lower flow-mediated dilatation (p = 0.01) compared to control groups. In contrast, sublingual nitroglycerine elicited a comparable vasodilatory response in the three groups. The augmentation index correlated significantly with pulse wave velocity and flow-mediated dilatation (R = 0.28 and R = -0.32, respectively, P < 0.05 for both). No significant correlations were observed between augmentation index or flow-mediated dilatation with age, body mass index (BMI), brachial blood pressure, heart rate, or metabolic parameters (plasma cholesterol, glucose, insulin, or insulin resistance). Birth weight maintained a significantly inverse correlation with the augmentation index (R = -0.51, p < 0.002) but not with flow-mediated dilatation. Our findings revealed a parallel decrease in arterial distensibility and endothelium-dependent dilatation in women with a history of pre-eclampsia compared to nulliparous women and women with a previous normal pregnancy. A high augmentation index was the most consistent alteration associated with a history of pre-eclampsia. The study supports the current view that the generalized arterial dysfunction associated with pre-eclampsia persists subclinically after delivery.

Conversion of laser energy to gas kinetic energy

NASA Technical Reports Server (NTRS)

Caledonia, G. E.

1977-01-01

Techniques for the gas-phase absorption of laser energy with ultimate conversion to heat or directed kinetic energy are reviewed. It is shown that the efficiency of resonance absorption by the vibration/rotation bands of the working gas can be enhanced by operating at sufficiently high pressures so that the linewidths of the absorbing transition exceed the line spacing. Within this limit, the gas can absorb continuously over the full spectral region of the band, and bleaching can be minimized since the manifold of molecular vibrational levels can simultaneously absorb the laser radiation.

Differential Scanning Calorimetry and Evolved Gas Analysis at Mars Ambient Conditions Using the Thermal Evolved Gas Analyzer (TEGA)

NASA Technical Reports Server (NTRS)

Musselwhite, D. S.; Boynton, W. V.; Ming, Douglas W.; Quadlander, G.; Kerry, K. E.; Bode, R. C.; Bailey, S. H.; Ward, M. G.; Pathare, A. V.; Lorenz, R. D.

2000-01-01

Differential Scanning Calorimetry (DSC) combined with evolved gas analysis (EGA) is a well developed technique for the analysis of a wide variety of sample types with broad application in material and soil sciences. However, the use of the technique for samples under conditions of pressure and temperature as found on other planets is one of current C development and cutting edge research. The Thermal Evolved Gas Analyzer (MGA), which was designed, built and tested at the University of Arizona's Lunar and Planetary Lab (LPL), utilizes DSC/EGA. TEGA, which was sent to Mars on the ill-fated Mars Polar Lander, was to be the first application of DSC/EGA on the surface of Mars as well as the first direct measurement of the volatile-bearing mineralogy in martian soil.

Visual impact assessment in British oil and gas developments

Treesearch

Dennis F. Gillespie; Brian D. Clark

1979-01-01

Development of oil and gas resource in the North Sea has led to the application of visual impact assessment techniques to onshore oil and gas developments in the United Kingdom. Formal visual impact assessment methods are needed to supplement landscape evaluations and site selection studies. Three major orientations of British visual impact assessments are: the...

Etching radical controlled gas chopped deep reactive ion etching

DOEpatents

Olynick, Deidre; Rangelow, Ivo; Chao, Weilun

2013-10-01

A method for silicon micromachining techniques based on high aspect ratio reactive ion etching with gas chopping has been developed capable of producing essentially scallop-free, smooth, sidewall surfaces. The method uses precisely controlled, alternated (or chopped) gas flow of the etching and deposition gas precursors to produce a controllable sidewall passivation capable of high anisotropy. The dynamic control of sidewall passivation is achieved by carefully controlling fluorine radical presence with moderator gasses, such as CH.sub.4 and controlling the passivation rate and stoichiometry using a CF.sub.2 source. In this manner, sidewall polymer deposition thicknesses are very well controlled, reducing sidewall ripples to very small levels. By combining inductively coupled plasmas with controlled fluorocarbon chemistry, good control of vertical structures with very low sidewall roughness may be produced. Results show silicon features with an aspect ratio of 20:1 for 10 nm features with applicability to nano-applications in the sub-50 nm regime. By comparison, previous traditional gas chopping techniques have produced rippled or scalloped sidewalls in a range of 50 to 100 nm roughness.

Beat frequency quartz-enhanced photoacoustic spectroscopy for fast and calibration-free continuous trace-gas monitoring

PubMed Central

Wu, Hongpeng; Dong, Lei; Zheng, Huadan; Yu, Yajun; Ma, Weiguang; Zhang, Lei; Yin, Wangbao; Xiao, Liantuan; Jia, Suotang; Tittel, Frank K.

2017-01-01

Quartz-enhanced photoacoustic spectroscopy (QEPAS) is a sensitive gas detection technique which requires frequent calibration and has a long response time. Here we report beat frequency (BF) QEPAS that can be used for ultra-sensitive calibration-free trace-gas detection and fast spectral scan applications. The resonance frequency and Q-factor of the quartz tuning fork (QTF) as well as the trace-gas concentration can be obtained simultaneously by detecting the beat frequency signal generated when the transient response signal of the QTF is demodulated at its non-resonance frequency. Hence, BF-QEPAS avoids a calibration process and permits continuous monitoring of a targeted trace gas. Three semiconductor lasers were selected as the excitation source to verify the performance of the BF-QEPAS technique. The BF-QEPAS method is capable of measuring lower trace-gas concentration levels with shorter averaging times as compared to conventional PAS and QEPAS techniques and determines the electrical QTF parameters precisely. PMID:28561065

TIGER TM : Intelligent continuous monitoring of gas turbines

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKay, I.; Hibbert, J.; Milne, R.

1998-07-01

The field of condition monitoring has been an area of rapid growth, with many specialized techniques being developed to measure or predict the health of a particular item of plant. Much of the most recent work has gone into the diagnosis of problems on rotating machines through the application of vibration analysis techniques. These techniques though useful can have a number of limiting factors, such as the need to install specialized sensors and measurement equipment, or the limited scope of the type of data measured. It was recognized in 1992, that the surveillance and condition monitoring procedures available for criticalmore » plant, such as gas turbines, were not as comprehensive as they might be and that a novel approach was required to give the operator the necessary holistic view of the health of the plant. This would naturally provide an assessment of the maintenance practices required to yield the highest possible availability without the need to install extensive new instrumentation. From the above objective, the TIGER system was designed which utilizes available data from the gas turbine control system or additionally the plant DCS to measure the behavior of the gas turbine and its associated sub systems. These measured parameters are then compared with an internal model of the turbine system and used to diagnose incorrect responses and therefore the item that is at fault, allowing the operator to quickly restart the turbine after a trip or perform condition based maintenance at the next scheduled outage. This philosophy has been built into the TIGER system and the purpose of this paper is to illustrate its functionality and some of the innovative techniques used in the diagnosis of real gas turbine problems. This is achieved by discussing three case studies where TIGER was integral in returning the plant to operation more quickly than can normally be expected.« less

Random-hole optical fiber evanescent-wave gas sensing.

PubMed

Pickrell, G; Peng, W; Wang, A

2004-07-01

Research on development of optical gas sensors based on evanescent-wave absorption in random-hole optical fibers is described. A process to produce random-hole optical fibers was recently developed that uses a novel in situ bubble formation technique. Gas molecules that exhibit characteristic vibrational absorption lines in the near-IR region that correspond to the transmission window for silica optical fiber have been detected through the evanescent field of the guided mode in the pore region. The presence of the gas molecules in the holes of the fiber appears as a loss at wavelengths that are characteristic of the particular gas species present in the holes. An experimental setup was constructed with these holey fibers for detection of acetylene gas. The results clearly demonstrate the characteristic absorptions in the optical spectra that correspond to the narrow-line absorptions of the acetylene gas, and this represents what is to our knowledge the first report of random-hole fiber gas sensing in the literature.

Practical Problems in the Cement Industry Solved by Modern Research Techniques

ERIC Educational Resources Information Center

Daugherty, Kenneth E.; Robertson, Les D.

1972-01-01

Practical chemical problems in the cement industry are being solved by such techniques as infrared spectroscopy, gas chromatography-mass spectrometry, X-ray diffraction, atomic absorption and arc spectroscopy, thermally evolved gas analysis, Mossbauer spectroscopy, transmission and scanning electron microscopy. (CP)

The Multiple Inert Gas Elimination Technique: A User’s Manual

DTIC Science & Technology

2016-02-11

These quantities are measured for inspired and expired oxygen and carbon dioxide, as well as minute ventilation . Expired Gas Sampling...Schematic of Ventilator /MIGET Sampling Circuit” (pp 28-30). By this mode, the ventilator is effectively , completely excluded from the sampling apparatus...connects the subject to the mixing box and the exhaust from the mixing box to the ventilator , temperature control is of the highest priority. The tubing

Advanced analytical techniques for the extraction and characterization of plant-derived essential oils by gas chromatography with mass spectrometry.

PubMed

Waseem, Rabia; Low, Kah Hin

2015-02-01

In recent years, essential oils have received a growing interest because of the positive health effects of their novel characteristics such as antibacterial, antifungal, and antioxidant activities. For the extraction of plant-derived essential oils, there is the need of advanced analytical techniques and innovative methodologies. An exhaustive study of hydrodistillation, supercritical fluid extraction, ultrasound- and microwave-assisted extraction, solid-phase microextraction, pressurized liquid extraction, pressurized hot water extraction, liquid-liquid extraction, liquid-phase microextraction, matrix solid-phase dispersion, and gas chromatography (one- and two-dimensional) hyphenated with mass spectrometry for the extraction through various plant species and analysis of essential oils has been provided in this review. Essential oils are composed of mainly terpenes and terpenoids with low-molecular-weight aromatic and aliphatic constituents that are particularly important for public health. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

PHIBSS: Unified Scaling Relations of Gas Depletion Time and Molecular Gas Fractions

NASA Astrophysics Data System (ADS)

Tacconi, L. J.; Genzel, R.; Saintonge, A.; Combes, F.; García-Burillo, S.; Neri, R.; Bolatto, A.; Contini, T.; Förster Schreiber, N. M.; Lilly, S.; Lutz, D.; Wuyts, S.; Accurso, G.; Boissier, J.; Boone, F.; Bouché, N.; Bournaud, F.; Burkert, A.; Carollo, M.; Cooper, M.; Cox, P.; Feruglio, C.; Freundlich, J.; Herrera-Camus, R.; Juneau, S.; Lippa, M.; Naab, T.; Renzini, A.; Salome, P.; Sternberg, A.; Tadaki, K.; Übler, H.; Walter, F.; Weiner, B.; Weiss, A.

2018-02-01

This paper provides an update of our previous scaling relations between galaxy-integrated molecular gas masses, stellar masses, and star formation rates (SFRs), in the framework of the star formation main sequence (MS), with the main goal of testing for possible systematic effects. For this purpose our new study combines three independent methods of determining molecular gas masses from CO line fluxes, far-infrared dust spectral energy distributions, and ∼1 mm dust photometry, in a large sample of 1444 star-forming galaxies between z = 0 and 4. The sample covers the stellar mass range log(M */M ⊙) = 9.0–11.8, and SFRs relative to that on the MS, δMS = SFR/SFR(MS), from 10‑1.3 to 102.2. Our most important finding is that all data sets, despite the different techniques and analysis methods used, follow the same scaling trends, once method-to-method zero-point offsets are minimized and uncertainties are properly taken into account. The molecular gas depletion time t depl, defined as the ratio of molecular gas mass to SFR, scales as (1 + z)‑0.6 × (δMS)‑0.44 and is only weakly dependent on stellar mass. The ratio of molecular to stellar mass μ gas depends on (1+z{)}2.5× {(δ {MS})}0.52× {({M}* )}-0.36, which tracks the evolution of the specific SFR. The redshift dependence of μ gas requires a curvature term, as may the mass dependences of t depl and μ gas. We find no or only weak correlations of t depl and μ gas with optical size R or surface density once one removes the above scalings, but we caution that optical sizes may not be appropriate for the high gas and dust columns at high z. Based on observations of an IRAM Legacy Program carried out with the NOEMA, operated by the Institute for Radio Astronomy in the Millimetre Range (IRAM), which is funded by a partnership of INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Aortic distensibility as a surrogate for intertwin pulse pressure differences in monochorionic pregnancies with and without twin-twin transfusion syndrome.

PubMed

Wohlmuth, C; Osei, F A; Moise, K J; Johnson, A; Papanna, R; Bebbington, M; Gardiner, H M

2016-08-01

Twin-twin transfusion syndrome (TTTS) complicates 10-15% of monochorionic diamniotic (MCDA) twin pregnancies. The donor response to hypovolemia allows the transfer of vasoactive mediators to the recipient, causing increased recipient afterload and hypertension. Our objective was to apply a novel speckle-tracking technique to measure the aortic fractional area change (AFAC) during the cardiac cycle in MCDA twins with and without TTTS, and identify intertwin differences in AFAC and parameters of cardiac function. High-frame rate four-chamber views of the fetal heart, including the mid-thoracic aorta, were collected prospectively in MCDA twin pairs referred to our center between June 2014 and April 2015. Using speckle-tracking software, the endovascular border of the aorta was traced manually during systole, with guidance on cardiac cycle timing by anatomical M-mode. AFAC, defined as the difference between maximum and minimum area divided by minimum area, expressed as a percentage, was calculated offline and averaged over three cardiac cycles. Tissue Doppler and displacement were used to measure long-axis cardiac function. Intra- and interclass correlation coefficients were used to test observer variability. Fifty-one MCDA twin pregnancies were included, comprising uncomplicated MCDA (n = 14), TTTS Stages 1/2 (n = 21) and TTTS Stages 3/4 (n = 16). Median gestational age was 20.4 (range, 16.2-27.5) weeks. Mean ± SD heart rate was 142.6 ± 7.2 bpm with no significant intertwin pair differences. AFAC was significantly higher in recipients than in donors of TTTS pairs (Stages 1/2: 72.3 ± 29.9% vs 43.7 ± 19.3%, P < 0.001; Stages 3/4: 75.2 ± 29.2% vs 42.5 ± 18.4%, P = 0.002), consistent with higher recipient pulse pressure. No intertwin differences in AFAC were seen in uncomplicated MCDA pairs. Inter- and intraclass correlation coefficients for AFAC were 0.894 and 0.888. AFAC correlated significantly with combined cardiac

Carotid Arterial Wall Dynamics During Gravity Changes on Partial-g Parabolic Flights

NASA Astrophysics Data System (ADS)

Leguy, C. A. D.; Beck, P.; Gauger, P.; Beck, L. E. J.; Limper, U.

2014-10-01

The investigation of systemic blood pressure (BP) responses under partial-g conditions is of particular importance with respect to post-space-flight orthostatic intolerance. In this study, changes in vessel diameter and wall distension of the common carotid artery (CCA) were assessed under graded gravity. Measurements were performed on 8 healthy subjects in standing position under lunar (0.16 g), Martian (0.38 g), 1.0 g and hypergravity (1.8 g) during partial-g parabolic flights. Data are reported as means ± SE estimated by linear mixed effects modeling. The CCA diameter was significantly enlarged under Martian and lunar-g (6.55 ± 0.2 and 6.54 ± 0.2 mm; p < 0.001 each) with respect to 1.0 g (6.39 ± 0.2 mm). The CCA distension showed significant enlargement under Martian-g (622 ± 91 μm) with respect to 1.0 g (603 ± 82 μm; p < 0.05). Furthermore, the distension was significantly lower under hyper-g with respect to 1.0 g (550 ± 88 μm; p < 0.001). These results show that rapid changes of gravitational stress induce significant modifications of hemodynamic parameters reflected in the CCA vessel wall diameter and distension. The increased vessel wall diameter under partial-g is likely due to the rise in mean BP at the CCA level caused by the absence of hydrostatic pressure and may trigger the baroreflex to maintain homeostatis. We can assume that the increase in distension during the partial-g phase originates from a larger stroke volume and enhanced BP reflections. Furthermore, this study demonstrates the reliability of functional high resolution vascular ultrasound technique during parabolic flights.

Improved enrichment culture technique for methane-oxidizing bacteria from marine ecosystems: the effect of adhesion material and gas composition.

PubMed

Vekeman, Bram; Dumolin, Charles; De Vos, Paul; Heylen, Kim

2017-02-01

Cultivation of microbial representatives of specific functional guilds from environmental samples depends largely on the suitability of the applied growth conditions. Especially the cultivation of marine methanotrophs has received little attention, resulting in only a limited number of ex situ cultures available. In this study we investigated the effect of adhesion material and headspace composition on the methane oxidation activity in methanotrophic enrichments obtained from marine sediment. Addition of sterilized natural sediment or alternatively the addition of acid-washed silicon dioxide significantly increased methane oxidation. This positive effect was attributed to bacterial adhesion on the particles via extracellular compounds, with a minimum amount of particles required for effect. As a result, the particles were immobilized, thus creating a stratified environment in which a limited diffusive gas gradients could build up and various microniches were formed. Such diffusive gas gradient might necessitate high headspace concentrations of CH 4 and CO 2 for sufficient concentrations to reach the methane-oxidizing bacteria in the enrichment culture technique. Therefore, high concentrations of methane and carbon dioxide, in addition to the addition of adhesion material, were tested and indeed further stimulated methane oxidation. Use of adhesion material in combination with high concentrations of methane and carbon dioxide might thus facilitate the cultivation and subsequent enrichment of environmentally important members of this functional guild. The exact mechanism of the observed positive effects on methane oxidation and the differential effect on methanotrophic diversity still needs to be explored.

Trace gas retrieval for limb DOAS under changing atmospheric conditions: The X-gas scaling method vs optimal estimation

NASA Astrophysics Data System (ADS)

Hueneke, Tilman; Grossmann, Katja; Knecht, Matthias; Raecke, Rasmus; Stutz, Jochen; Werner, Bodo; Pfeilsticker, Klaus

2016-04-01

Changing atmospheric conditions during DOAS measurements from fast moving aircraft platforms pose a challenge for trace gas retrievals. Traditional inversion techniques to retrieve trace gas concentrations from limb scattered UV/vis spectroscopy, like optimal estimation, require a-priori information on Mie extinction (e.g., aerosol concentration and cloud cover) and albedo, which determine the atmospheric radiative transfer. In contrast to satellite applications, cloud filters can not be applied because they would strongly reduce the usable amount of expensively gathered measurement data. In contrast to ground-based MAX-DOAS applications, an aerosol retrieval based on O4 is not able to constrain the radiative transfer in air-borne applications due to the rapidly decreasing amount of O4 with altitude. Furthermore, the assumption of a constant cloud cover is not valid for fast moving aircrafts, thus requiring 2D or even 3D treatment of the radiative transfer. Therefore, traditional techniques are not applicable for most of the data gathered by fast moving aircraft platforms. In order to circumvent these limitations, we have been developing the so-called X-gas scaling method. By utilising a proxy gas X (e.g. O3, O4, …), whose concentration is either a priori known or simultaneously in-situ measured as well as remotely measured, an effective absorption length for the target gas is inferred. In this presentation, we discuss the strengths and weaknesses of the novel approach along with some sample cases. A particular strength of the X-gas scaling method is its insensitivity towards the aerosol abundance and cloud cover as well as wavelength dependent effects, whereas its sensitivity towards the profiles of both gases requires a priori information on their shapes.

Fabrication and characterisation of ligand-functionalised ultrapure monodispersed metal nanoparticle nanoassemblies employing advanced gas deposition technique

NASA Astrophysics Data System (ADS)

Geremariam Welearegay, Tesfalem; Cindemir, Umut; Österlund, Lars; Ionescu, Radu

2018-02-01

Here, we report for the first time the fabrication of ligand-functionalised ultrapure monodispersed metal nanoparticles (Au, Cu, and Pt) from their pure metal precursors using the advanced gas deposition technique. The experimental conditions during nanoparticle formation were adjusted in order to obtain ultrafine isolated nanoparticles on different substrates. The morphology and surface analysis of the as-deposited metal nanoparticles were investigated using scanning electron microscopy, x-ray diffraction and Fourier transform infra-red spectroscopy, which demonstrated the formation of highly ordered pure crystalline nanoparticles with a relatively uniform size distribution of ∼10 nm (Au), ∼4 nm (Cu) and ∼3 nm (Pt), respectively. A broad range of organic ligands containing thiol or amine functional groups were attached to the nanoparticles to form continuous networks of nanoparticle-ligand nanoassemblies, which were characterised by scanning electron microscopy and x-ray photoelectron spectroscopy. The electrical resistance of the functional nanoassemblies deposited in the gap spacing of two microfabricated parallel Au electrodes patterned on silicon substrates ranged between tens of kΩ and tens of MΩ, which is suitable for use in many applications including (bio)chemical sensors, surface-enhanced Raman spectroscopy and molecular electronic rectifiers.

Preliminary measurement of gas concentrations of perfluropropane using an analytical weighing balance.

PubMed

Clarkson, Douglas McG; Manna, Avinish; Hero, Mark

2014-02-01

We describe the use of an analytical weighing balance of measurement accuracy 0.00001g for determination of concentrations of perfluropropane (C3F8) gas used in ophthalmic surgical vitrectomy procedures. A range of test eyes corresponding to an eye volume of 6.1ml were constructed using 27 gauge needle exit ducts and separately 20 gauge (straight) and 23 gauge (angled) entrance ports. This method allowed determination of concentration levels in the sample preparation syringe and also levels in test eyes. It was determined that a key factor influencing gas concentrations accuracy related to the method of gas fill and the value of dead space of the gas preparation/delivery system and with a significant contribution arising from the use of the particle filter. The weighing balance technique was identified as an appropriate technique for estimation of gas concentrations. Copyright © 2013 IPEM. Published by Elsevier Ltd. All rights reserved.

A nonlinear model for gas chromatograph systems

NASA Technical Reports Server (NTRS)

Feinberg, M. P.

1975-01-01

Fundamental engineering design techniques and concepts were studied for the optimization of a gas chromatograph-mass spectrometer chemical analysis system suitable for use on an unmanned, Martian roving vehicle. Previously developed mathematical models of the gas chromatograph are found to be inadequate for predicting peak heights and spreading for some experimental conditions and chemical systems. A modification to the existing equilibrium adsorption model is required; the Langmuir isotherm replaces the linear isotherm. The numerical technique of Crank-Nicolson was studied for use with the linear isotherm to determine the utility of the method. Modifications are made to the method eliminate unnecessary calculations which result in an overall reduction of the computation time of about 42 percent. The Langmuir isotherm is considered which takes into account the composition-dependent effects on the thermodynamic parameter, mRo.

Stagnation pressure probe. [for measuring pressure of supersonic gas streams

NASA Technical Reports Server (NTRS)

Goodyer, M. J. (Inventor)

1974-01-01

A method and apparatus for measuring the stagnation pressure of supersonic velocity gas streams without the generation of shock waves which interfere with such measurements are given. The technique is insensitive to the type of gas and Mach number and is therefore particularly useful in the study of jet engine exhausts.

Gas detection by correlation spectroscopy employing a multimode diode laser.

PubMed

Lou, Xiutao; Somesfalean, Gabriel; Zhang, Zhiguo

2008-05-01

A gas sensor based on the gas-correlation technique has been developed using a multimode diode laser (MDL) in a dual-beam detection scheme. Measurement of CO(2) mixed with CO as an interfering gas is successfully demonstrated using a 1570 nm tunable MDL. Despite overlapping absorption spectra and occasional mode hops, the interfering signals can be effectively excluded by a statistical procedure including correlation analysis and outlier identification. The gas concentration is retrieved from several pair-correlated signals by a linear-regression scheme, yielding a reliable and accurate measurement. This demonstrates the utility of the unsophisticated MDLs as novel light sources for gas detection applications.

Inter-comparison of laser photoacoustic spectroscopy and gas chromatography techniques for measurements of ethene in the atmosphere.

PubMed

Kuster, William C; Harren, Frans J M; de Gouw, Joost A

2005-06-15

Laser photoacoustic spectroscopy (LPAS) is highly suitable for the detection of ethene in air due to the overlap between its strongest absorption lines and the wavelengths accessible by high-powered CO2 lasers. Here, we test the ability of LPAS to measure ethene in ambient air by comparing the measurements in urban air with those from a gas chromatography flame-ionization detection (GC-FID) instrument. Over the course of several days, we obtained quantitative agreement between the two measurements. Over this period, the LPAS instrument had a positive offset of 330 +/- 140 pptv (parts-per-trillion by volume) relative to the GC-FID instrument, possibly caused by interference from other species. The detection limit of the LPAS instrument is currently estimated around 1 ppbv and is limited by this offset and the statistical noise in the data. We conclude that LPAS has the potential to provide fast-response measurements of ethene in the atmosphere, with significant advantages over existing techniques when measuring from moving platforms and in the vicinity of emission sources.

Application of LIF technique for the space- and time-resolved monitoring of pollutant gas decomposition in nonthermal plasma reactors

NASA Astrophysics Data System (ADS)

Mizeraczyk, Jerzy; Ohkubo, Toshikazu; Kanazawa, Seiji; Kocik, Marek

2003-10-01

Laser-induced fluorescence (LIF) technique aided by intensified CCD light signal detection and fast digital image processing is demonstrated to be a useful diagnostic method for in-situ observation of the discharge-induced plasma-chemistry processes responsible for NOx(NO + NO2) decomposition occurring in non-thermal plasma reactors. In this paper a method and results of the LIF measurement of two-dimensional distribution of the ground-state NO molecule density inside a DC positive streamer corona reactor during NO removal from a flue gas simulator [air/NO(up to 300 ppm)] are presented. Either a needle-to-plate or nozzle-to-plate electrode system, having an electrode gap of 30-50 mm was used for generating the corona discharge in the reactor. The LIF monitoring of NO molecules was carried out under the steady-state DC corona discharge condition. The laser-induced fluorescence on the transition NO X2Π(v"=0)<--A2Σ+(v'=0) at λ=226nm was chosen for monitoring ground-state NO molecules in the reactor. This transition was induced by irradiation of the NO molecules with UV laser pulses generated by a laser system consisted of a XeF excimer laser, dye laser and BBO crystal. The laser pulses from the XeF excimer laser (Lambda Physik, Complex 150, λ=351 nm) pumped the dye laser (Lambda Physik, Scanmate) with Coumarin 47 as a dye, which generated the laser beam of a wavelength turned around λ=450 nm. Then, the tuned dye laser beam pumped the BBO crystal in which the second harmonic radiation of a wavelength correspondingly tuned around λ=226 nm was generated. The 226-nm UV laser pulses of energy of 0.8-2 mJ and duration of about 20 ns were transformed into the form of the so-called laser sheet (width of 1 mm, height of 30-50 mm) which passed between the electrodes through the operating gas. The obtained results, presented in the form of images, which illustrated the two-dimensional distributions of NO molecule concentration in the non-thermal reactor, showed that the

A survey of gas-side fouling in industrial heat-transfer equipment

NASA Astrophysics Data System (ADS)

Marner, W. J.; Suitor, J. W.

1983-11-01

Gas-side fouling and corrosion problems occur in all of the energy intensive industries including the chemical, petroleum, primary metals, pulp and paper, glass, cement, foodstuffs, and textile industries. Topics of major interest include: (1) heat exchanger design procedures for gas-side fouling service; (2) gas-side fouling factors which are presently available; (3) startup and shutdown procedures used to minimize the effects of gas-side fouling; (4) gas-side fouling prevention, mitigation, and accommodation techniques; (5) economic impact of gas-side fouling on capital costs, maintenance costs, loss of production, and energy losses; and (6) miscellaneous considerations related to gas-side fouling. The present state-of-the-art for industrial gas-side fouling is summarized by a list of recommendations for further work in this area.