Quantitative flow visualization of fluidized-bed heat exchanger by neutron radiography.

Quantitative flow visualization of a gas-solid fluidized-bed installed vertical tube-bank has been successfully conducted using neutron radiography and image processing technique. The quantitative data of void fraction distribution as well as the fluctuation data are presented. The time-averaged void fraction is well correlated by the drift-flux model. The bubbles formed in the bed, rise along the vertical tubes and the observed bubble size is smaller than that in a free bubbling bed without tube-banks. The bubble diameter is well correlated by the modified Mori and Wen's correlation taking into account the pitch of tube arrangement. The bubble rise velocity is also well correlated by applying the drift-flux model. These results are consistent for both bed materials of Geldart's B- and A-particles, while the bubble size is significantly different between two kinds of particles.     

Evaluation of the bubble point test of a 0.22-μm membrane filter used for the sterilizing filtration of PET radiopharmaceuticals

Objective

We developed a bubble point test kit and investigated the bubble point test of a 0.22-μm membrane filter used for the sterilizing filtration of [¹⁸F]FDG, [¹¹C]MET and [¹¹C]PIB. The bubble point test of the Millex-GS vented filter was often difficult due to air leakage from the vented portion of this filter. Therefore, to close the vented portion of this filter simply and reliably, we investigated the use of various materials.

Methods

The bubble point test of the Millex-GS vented filter was performed by closing the vented portion of this filter with various materials, such as vinyl tape, plastic paraffin film (parafilm), urethane elastomer adhesive mat and polyethylene foam cushion tape. Gradually, the plunger inside a syringe filled with air was pushed down to increase the pressure on the pressure gauge and the bubble point test kit. Simultaneously, the pressure when a continuous stream of air bubbles that appeared out of the 0.22-μm membrane filter was measured as the product-wetted bubble point value. Then, the plunger inside a syringe filled with 10 mL of water was pushed down to wash the 0.22-μm membrane filter. As in the case in the above-mentioned method of measuring the product-wetted bubble point, the water-wetted bubble point value was measured.

Results

The use of the polyethylene foam cushion tape and a double clip could easily and reliably prevent air leakage from the vented portion of the Millex-GS vented filter. In the bubble point test of [¹⁸F]FDG, [¹¹C]MET and [¹¹C]PIB, the product-wetted bubble point values were 382.7 ± 6.9 kPa, 385.4 ± 6.2 kPa and 351.6 ± 7.6 kPa, respectively. The bubble point ratio was used to determine the minimum product-wetted bubble point value. All results of the product-wetted bubble point test were beyond the minimum product-wetted bubble point value (334.4 kPa ([¹⁸F]FDG), 334.4 kPa ([¹¹C]MET) and 310.3 kPa ([¹¹C]PIB)). Then, the water-wetted bubble point values were 396.5 ± 8.3 kPa, 395.8 ± 8.3 kPa and 390.3 ± 7.6 kPa, respectively. All results of the water-wetted bubble point test were beyond the filter manufacturer’s minimum bubble point specification (344.8 kPa).

Conclusions

The bubble point test technique using the bubble point test kit was practical for routine quality control tests of PET radiopharmaceuticals.     

Gastrostomy Tube Placement Without Nasogastric Tube: A Retrospective Evaluation in 85 Patients

Purpose

Our study evaluated techniques for percutaneous gastrostomy (G)-tube placement without the use of a nasogastric (NG) tube. Instead, direct puncture of a physiologic air bubble or effervescent-enhanced gastric bubble distention was performed in patients with upper digestive tract obstruction (UDTO) or psychological objections to NG tubes.

Materials and Methods

A total of 886 patients underwent G-tube placement in our department during a period of 7?years. We present our series of 85 (9.6%) consecutive patients who underwent percutaneous G-tube placement without use of an NG tube.

Results

Of these 85 patients, fluoroscopic guided access was attempted by direct puncture of a physiologically present gastric air bubble in 24 (28%) cases. Puncture of an effervescent-induced large gastric air bubble was performed in 61 (72%) patients. Altogether, 82 (97%) of 85 G tubes were successfully placed in this fashion. The three failures comprised refusal of effervescent, vomiting of effervescent, and one initial tube misplacement when a deviation from our standard technique occurred.

Conclusion

The described techniques compare favorably with published large series on G-tube placement with an NG tube in place. The techniques are especially suited for patients with UDTO due to head, neck, or esophageal malignancies, but they should be considered as an alternative in all patients. Direct puncture of effervescent-enhanced gastric bubble distention is a safe, patient-friendly and effective technique.     

静脉注射钙镁离子对家兔高空减压血流中气泡生成的影响

观察了静脉注射硫酸镁和葡萄糖酸钙溶液对家兔高空减压时血流中气泡生成的影响。实验采用3×3拉丁方设计，共进行了4组，36次实验。硫酸镁溶液浓度为12.5％，葡萄糖酸钙浓度为7．5％。减压高度12000m，停留时间20min。用多普勒超声检测心前区血流中气泡。结果表明，注射硫酸镁和葡萄糖酸钙后气泡生成量和出现时间无明显变化。提示单纯血液镁、钙离子升高不是静脉气泡生成的易感因素。     

Significance of delayed symptom onset and bubble growth in altitude decompression sickness

Three characteristics of altitude induced decompression sickness (DCS) are: 1) symptoms occur some time after arrival at altitude; 2) symptoms seldom occur below 18,000 ft, even though bubbles are frequently detected at that low altitude; 3) symptoms seldom occur after 4 h at altitude. These observations could be explained if it were postulated that bubbles must reach a threshold size before symptoms of DCS occur. In vitro techniques were used in this study to measure bubble growth at various altitudes. The results indicate that although the growth rate of bubbles depends strongly on the altitude where they form, bubble growth requires time. This helps explain the first observation above. We found that bubbles stop growing early at a small size below 18,000 ft. This helps explain the second observation above. Finally, we found that bubbles stop growing when the fluid immediately surrounding the bubble is cleared of supersaturated gas regardless of the fluid composition a few centimeters from the bubble. This helps explain the last observation above.     

The gastric bubble: roentgen observations

The appearance of the stomach bubble provides many clues to underlying thoracoabdominal disorders. Illustrated in this article are (1) the major complications of large hiatal hernias: intrathoracic gastric volvulus and ulceration; (2) diaphragmatic abnormalities including inversion of the hemidiaphragm and intrathoracic displacement of abdominal contents because of diaphragmatic laceration or congenital herniation; (3) extrinsic displacement of the stomach bubble by splenomegaly (the occurrence of which in association with radiographic abnormalities in the chest--cardiomegaly, interstitial lung disease, mediastinal or hilar adenopathy--helps form a differential diagnosis); and (4) situs abnormalities for the analysis of which a simplified schema is presented.     

Exercise during a 3-min decompression stop reduces postdive venous gas bubbles

PURPOSE: Decompression sickness is initiated by the formation of gas bubbles in tissue and blood if the divers return to surface pressure too fast. The effect of exercise before, during, and after dive on bubble formation is still controversial. We have reported recently that strenuous aerobic exercise 24 h before simulated dive ameliorates venous bubble formation. The objective of this field study was to evaluate whether mild, continuous exercise during decompression has a similar impact. METHODS: Ten healthy, military male divers performed an open-sea field dive to 30 m of sea water breathing air, remaining at pressure for 30 min. During the bottom and decompression the subjects performed fin underwater swimming at about 30% of maximal oxygen uptake. Each diver underwent two randomly assigned dives, one with and one without exercise during the 3-min decompression period. Monitoring of venous gas emboli was performed in the right heart with ultrasonic scanner every 20 min for 60 min after reaching surface pressure in supine rest and during forced two-cough procedure. RESULTS: The study demonstrates that a mild, continuous exercise during decompression significantly reduced the average number of bubbles in the pulmonary artery from 0.9 +/- 0.8 to 0.3 +/- 0.5 bubbles per square centimeter in supine rest, as well as during two-cough procedure, which decreased from 4.6 +/- 4.5 to 0.9 +/- 0.9 bubbles per square centimeter. No symptoms of decompression sickness were observed in any subject. CONCLUSION: These results, obtained in the field conditions, indicate that a mild, underwater swimming during a 3-min decompression period reduces postdive gas bubbles formation.     

“Air bubble”: a new diagnostic CT sign of perforated pulmonary hydatid cyst

The greatest difficulty in the CT diagnosis of perforated pulmonary hydatid cyst (PPHC) is the increase in the attenuation numbers following infection. Because of the solid density of infected hydatid cysts, the differentiation from an abscess or neoplasm is usually impossible. The aim of this study was to evaluate the value of “air bubble” as a new CT sign in the diagnosis of PPHC. Sixty-five patients (28 men and 37 women) with PPHC were included in the study. As a control group, 55 patients who had malignant (n = 36) or non-malignant (n = 19) pulmonary diseases were also examined. Radiological diagnosis with classical CT findings was made in only 38 of 65 patients (58.5 %) with PPHC. Air bubble sign was positive in 54 of the patients with PPHC (sensitivity 83.1 %) but only 3 of 55 patients in control group (specificity 94.5 %). When we analyzed the CT scans with classical CT findings including air bubble, the diagnosis of PPHC was made in 61 of patients (93.8 %). It is concluded that “air bubble sign” is a valuable CT finding in the diagnosis of PPHC. Received: 3 September 1997; Revision received: 22 May 1998; Accepted: 5 August 1998     

Influence of bubble size distribution on the echogenicity of ultrasound contrast agents: a study of SonoVue

RATIONALE AND OBJECTIVES: To study the relative contributions of different bubble size classes to SonoVue's echogenicity in fundamental acoustic imaging modes. SonoVue is a contrast agent, previously known as BR1, with a bubble size distribution extending from approximately 0.7 to 10 microm. METHODS: A model for the acoustic response of SonoVue was determined and validated for a set of experimental data. This model was used to simulate the acoustic response of a standard batch of SonoVue as the sum of responses of non-overlapping bubble size classes. RESULTS: The simulation was first validated for a standard SonoVue bubble size distribution. When this distribution was considered as five size classes with equal numbers of bubbles, it was found that bubbles smaller than 2 microm accounted for 60% of the total number but contained only 5% of the total gas volume. The simulation results indicated marked differences in the acoustic contributions from these classes, with 80% of the acoustic efficacy provided by bubbles 3 to 9 microm in diameter. The study also compared bubble distributions in number, surface, and volume, with the distribution computed in terms of acoustic efficacy. CONCLUSIONS: This study shows why bubble volume is a much better indicator of SonoVue's efficacy than is bubble count. A low threshold in diameter was found for SonoVue microbubbles at approximately 2 microm, under which size bubbles do not contribute appreciably to the echogenicity at medical ultrasound frequencies.     

被动吸烟对豚鼠高空减压气泡生成影响的初步观察

观察了３０只豚鼠于密闭舱内被动吸入卷烟烟雾对随后高空减压心前区气泡出现的影响。结果表明：在上述２种吸入卷烟烟雾的条件下，减压气泡的首次出现时间和气泡等级与对照组相比无显著差异。初步提示减压露前短时间大量吸烟不会影响高空减压病的发生。     

Reactivity of hydroxybenzoic acids in the hydrogen-isotope exchange reaction.

The hydrogen-isotope exchange reaction (T-for-H exchange reaction) between tritiated water vapor (HTO vapor) and 3-hydroxy-4-methoxybenzoic acid (and it's analog; 4-hydroxy-3-methoxybenzoic acid) were observed at 50 and 70 degrees C in a gas-solid system to reveal the reactivity of a functional group in an aromatic compound having two substituents in the aromatic ring. Further, it was shown that (a) the reactivity of the compounds used in this work follows the Hammett's rule, and (b) the reactivity of trisubstituted aromatic compound could be analyzed by applying the additive property of the Hammett's rule even if the compound contains a substituent at the ortho-position.     

Use of pressure-hold test for sterilizing filter membrane integrity in radiopharmaceutical manufacturing

The bubble point test is the de facto standard for postproduction filter membrane integrity test in the radiopharmaceutical community. However, the bubble point test depends on a subjective visual assessment of bubbling rate that can be obscured by significant diffusive gas flows below the manufacturer's prescribed bubble point. To provide a more objective means to assess filter membrane integrity, this study evaluates the pressure-hold test as an alternative to the bubble point test. In our application of the pressure-hold test, the nonsterile side of the sterilizing filter is pressurized to 85% of the predetermined bubble point with nitrogen, the filter system is closed off from the pressurizing gas and the pressure is monitored over a prescribed time interval. The drop in pressure, which has a known relationship with diffusive gas flow, is used as a quantitative measure of membrane integrity. Characterization of the gas flow vs. pressure relationship of each filter/solution combination provides an objective and quantitative means for defining a critical value of pressure drop over which the membrane is indicated to be nonintegral. The method is applied to sterilizing filter integrity testing associated with the commonly produced radiopharmaceuticals, [¹⁸F]FDG and [¹¹C]PIB. The method is shown to be robust, practical and amenable to automation in radiopharmaceutical manufacturing environments (e.g., hot cells).     

Early diagnostic clues in neonatal chronic gastric volvulus

Purpose

Neonatal gastric volvulus (GV) is a rare clinical entity with a challenging diagnosis. In this study, we aimed to identify clinical and radiological findings to aid in early diagnosis in neonatal GV.

Materials and methods

The medical records of all neonates with GV were retrospectively reviewed. Diagnosis was made based on clinical findings and radiological images, and was documented by an upper gastrointestinal (UGI) contrast study.

Results

A total of eight neonates were included in the study. The most common clinical presentations were non-bilious vomiting and epigastric distention. The findings highly suggestive for GV in plain radiographs include gastric double bubble, abnormal gastric distention despite a nasogastric tube, distended stomach lying in a horizontal plane and an air-fluid level in the epigastrium.

Conclusion

GV should be suspected in any newborn with non-bilious vomiting and epigastric distention. It is also important to focus on the clues in the plain radiographs. Gastric double bubble, abnormal gastric distention despite a nasogastric tube, distended stomach lying in a horizontal plane and an air-fluid level in the epigastrium must alert the physicians to the possibility of GV.     

Pre-treatment with hyperbaric oxygenation reduces bubble formation and platelet activation

Abstract Bubble formation and platelet activation are major factors contributing to decompression sickness. We hypothesized that pretreatment with hyperbaric oxygen immediately before a dive may reduce bubble formation and platelet activation in humans. Five healthy volunteer subjects (1 female and 4 males; age, 33.6±2.9 years; height, 170±3 cm; weight, 71±8 kg, body mass index, 24.5±22.0 kg/m²) participated in this study with a 4-day protocol. On day 1, a multiplace hyperbaric chamber was used to compress all subjects with air to 4 atmosphere absolute (ATA) for 25 minutes; they were then decompressed to surface pressure at a rate of 10 m/min. Once surface pressure was reached, they were monitored with precordial ultrasonic Doppler at 20 min, 50 min and 80 min. Venous blood samples were obtained immediately before and after pressure exposure. On day 2, all subjects were compressed at 1.6 ATA for 45 min with 100% oxygen; they were then decompressed to surface pressure at a rate of 10 m/min. As soon as they reached surface pressure, they were immediately exposed to the same compression-decompression protocol as day 1; blood samples were taken after the second pressure exposure. Platelet activation was examined before and after exposure. On days 3 and 4, we inverted the protocol to minimize the influence of the first immersion on bubble formation. In comparison to the standard compression protocol, compression after hyperbaric oxygenation led to significantly reduced bubble numbers and platelet activation (11.4%±0.7% vs. 5.4%±0.5%, p<0.05). This study shows that hyperbaric oxygenation pretreatment significantly reduces decompression-induced bubble formation and platelet activation. Hyperbaric oxygenation pretreatment may reduce the risk of decompression sickness in at-risk activities.     

Optimization of detector positioning in the radioactive particle tracking technique

The radioactive particle tracking (RPT) technique is a non-intrusive experimental velocimetry and tomography technique extensively applied to the study of hydrodynamics in a great variety of systems. In this technique, arrays of scintillation detector are used to track the motion of a single radioactive tracer particle emitting isotropic γ-rays. This work describes and applies an optimization strategy developed to find an optimal set of positions for the scintillation detectors used in the RPT technique. This strategy employs the overall resolution of the detectors as the objective function and a mesh adaptive direct search (MADS) algorithm to solve the optimization problem. More precisely, NOMAD, a C++ implementation of the MADS algorithm is used. First, the optimization strategy is validated using simple cases with known optimal detector configurations. Next, it is applied to a three-dimensional axisymmetric system (i.e. a vertical cylinder, which could represent a fluidized bed, bubble column, riser or else). The results obtained using the optimization strategy are in agreement with what was previously recommended by Roy et al. (2002) for a similar system. Finally, the optimization strategy is used for a system consisting of a partially filled cylindrical tumbler. The application of insights gained by the optimization strategy is shown to lead to a significant reduction in the error made when reconstructing the position of a tracer particle. The results of this work show that the optimization strategy developed is sensitive to both the type of objective function used and the experimental conditions. The limitations and drawbacks of the optimization strategy are also discussed.     

On the parameters affecting the sensitivity of MR measures of pressure with microbubbles.

Recently, it has been suggested that gas encapsulated distensible microbubbles may serve as pressure probes in the MR field through the relationship between bubble size and 1/T(2) or 1/T(*)(2). Currently, in vivo application of this technique is hindered by the ability of T(2) or T(*)(2) to detect pressure changes that are clinically relevant. This work identifies and characterizes, through numerical simulations, the set of parameters which optimize the ability of this technique to detect small pressure changes. Results show that when the bubbles do not interact magnetically, the T(2)- and T(*)(2)-based measurements of pressure are strongly influenced by the bubble size at atmospheric pressure, static magnetic field strength, magnitude of the susceptibility difference between the encapsulated gas and plasma, bubble volume fraction, and the refocusing interval. In particular, to detect clinically relevant pressure changes, microbubbles need to be approximately 2-3 microm in radius, distributed at a volume fraction of 0.15%, and have a volumetric magnetic susceptibility difference of at least 34 ppm.     

Exogenous nitric oxide and bubble formation in divers

PURPOSE: Prevention of bubble formation is a central goal in standard decompression procedures. Previously we have shown that exercise 20-24 h prior to a dive reduces bubble formation and increases survival in rats exposed to a simulated dive. Furthermore, we have demonstrated that nitric oxide (NO) may be involved in this protection; blocking the production of NO increases bubble formation while giving rats a long-lasting NO donor 20 h and immediately prior to a dive reduces bubble formation. This study determined whether a short-lasting NO donor, nitroglycerine, reduced bubble formation after standard dives and decompression in man. METHODS: A total of 16 experienced divers were randomly assigned into two groups. One group performed two dives to 30 m of seawater (msw) for 30 min breathing air, and performed exercise at an intensity corresponding to 30% of maximal oxygen uptake during the bottom time. The second group performed two simulated dives to 18 msw for 80 min breathing air in a hyperbaric chamber, and remained sedentary during the bottom period. The first dive for each diver served as the control dive, whereas the divers received 0.4 mg of nitroglycerine by oral spray 30 min before the second dive. Following the dive, gas bubbles in the pulmonary artery were recorded using ultrasound. RESULTS: The open-water dive resulted in significantly more gas bubbles than the dry dive (0.87 +/- 1.3 vs 0.12 +/- 0.23 bubbles per square centimeter). Nitroglycerine reduced bubble formation significantly in both dives from 0.87 +/- 1.3 to 0.32 +/- 0.7 in the in-water dive and from 0.12 +/- 0.23 to 0.03 +/- 0.03 bubbles per square centimeter in the chamber dive. CONCLUSION: The present study demonstrates that intake of a short-lasting NO donor reduces bubble formation following decompression after different dives.     

Prophylactic statins as a possible method to decrease bubble formation in diving

INTRODUCTION: Nitric oxide (NO) may decrease bubble formation in diving. Statin medications are attractive potential options to increase NO. Statins exhibit a proven safety profile, and possess a myriad of pleiotropic properties improving vascular endothelial function. Additionally, statin-mediated lipid reduction may reduce bubble generation via alterations in plasma surface tension. We investigated the efficacy of atorvastatin as a pharmacological intervention to reduce the risk of bubble formation after diving, a surrogate for decompression sickness (DCS). METHODS: There were 16 trained military divers who completed a provacative hyperbaric chamber dive protocol after taking either 80-mg of atorvastatin or placebo for 4 d. Subjects completed the alternate medication regimen no sooner than 2 wk. After each dive, subjects were subjected to precordial trans-thoracic echocardiographic exams via standardized protocols. Bubbles were graded via a non-parametric, ordinal grading system and statistically analyzed via Wilcoxon signed-rank tests. RESULTS: We found no within subject differences for the maximum bubble grade scores (z = 0.00, p = 1.00, n=16). Low-density lipoprotein (LDL), and total cholesterol (TC) levels decreased significantly (107.6 +/- 26.2 to 79.3 +/- 21.9 mg x dl(-1) and 175 +/- 20.9 to 147 +/- 22.4 mg x dl(-1), respectively) 1-2 wk post statin administration. Age, bioelectrical impedance (BEI), TC, LDL, potassium, and calcium demonstrated positive correlations to placebo bubble grades. DISCUSSION: Prophylactic 80-mg atorvastatin administration for 4 d failed to reduce the number of intravascular bubbles observed following a 60-ft, 80-min dry chamber dive despite significant acute reductions in lipid levels. Several hypotheses may explain why statins failed to decrease bubble volume: (1) differential influence of statins on the venous vs. arterial vasculature; (2) failure to elicit an improvement in endothelial function and, therefore, the hypothesized endothelial conditioning in younger patients possessing normal baseline; and (3) the ordinal grading system encompassing a substantial variation in bubble volume (bubbles Scm(-2)).     

放射性球囊内气泡对血管组织剂量分布的影响

目的：计算放射性球囊治疗冠状动脉再狭窄时球囊内气泡对血管的剂量分布影响。方法：采用Prestwich的剂量点核函数计算球囊周围的剂量分布，计算体积为0.02mL的气泡位于球囊壁中心和边缘两种情况下对球囊周围组织的剂量分布影响，并与无气泡的液体球囊比较。结果：气泡在球囊壁中心时，影响范围为4mm,球囊两侧的剂量不均匀最大可达38％；在边缘时，影响范围为6mm，剂量不均匀达47％。结论：球囊内气泡对血管组织的剂量分布有影响。     

新生儿十二指肠梗阻59例X线分析

目的　探讨新生儿十二指肠梗阻的X线表现。资料与方法　回顾性分析 5 9例新生儿十二指肠梗阻的临床及X线资料 ,其中肠旋转不良 2 7例 ,十二指肠闭锁 2 2例 ,十二指肠狭窄 5例 ,环状胰腺 1例 ,肠旋转不良合并十二指肠闭锁 4例。结果　平片主要表现为单泡 (2 /5 9)、双泡 (48/5 9)、三泡 (5 /5 9)征 ,4 8例双泡征中 14例Dd/Ds(十二指肠泡直径 /胃泡直径 )≥ 1.0 ,其中完全性梗阻 13例 ,与不全性梗阻 1例有显著差异 (P <0 .0 1)。上消化道钡餐显示梗阻端形态呈圆顶状 32例 ,鸟嘴状 2例 ,束腰状 6例 ,不规则状 19例 ;14例显示空肠位置异常。钡灌肠显示盲肠位置异常 7例 (7/10 )。结论　双泡征是十二指肠梗阻最常见的X线征象 ;Dd/Ds≥ 1.0时 ,提示完全性梗阻 ;梗阻端形态对判断十二指肠梗阻的病因帮助不大