Molecular diameters of rarefied gases.

Molecular diameters are an important property of gases for numerous scientific and technical disciplines. Different measurement techniques for these diameters exist, each delivering a characteristic value. Their reliability in describing the flow of rarefied gases, however, has not yet been discussed, especially the case for the transitional range between continuum and ballistic flow. Here, we present a method to describe gas flows in straight channels with arbitrary cross sections for the whole Knudsen range by using a superposition model based on molecular diameters. This model allows us to determine a transition diameter from flow measurement data that paves the way for generalized calculations of gas behaviour under rarefied conditions linking continuum and free molecular regime.

A torsional sub-milli-Newton thrust balance based on a spring leaf strain gauge sensor.

The development of a torsional thrust balance with a spring leaf sensor based on strain gauges is described in the present work. The balance is capable of measuring thrust forces up to 225 mN with micro-Newton resolution. Steady state thrust force is hereby measured via displacement of the balance arm, which in return leads to a displacement of the sensor. The strain induced by the force on the flexure member of the sensor is measured using strain gauges. The development of the sensor and the dynamic behavior of the balance are based on analytical analysis. The oscillatory motion of the balance arm is damped by a passive eddy current damper. An automated calibration mechanism with a pulley and calibration weights is used to calibrate the balance prior to measurement. Atmospheric as well as in situ calibration, single and multiple calibration runs with automatic averaging of calibration coefficients, is possible at all operational stages. The calibration of the balance exhibits excellent linearity and repeatability, while the dynamic behavior shows some deviations from the analytical prediction. The sensor exhibits low noise, with an estimated resolution within 15 µN. A state-of-the-art ratio of resolution to measurement range is achieved. As a conclusion, a series of thrust measurements in the range of 29 µN-37.04 mN are presented and briefly discussed.

A comprehensive systematic review of testicular germ cell tumor surveillance.

BACKGROUND: Testicular cancer is the most common malignancy in men aged 15-34, and its incidence has been increasing over the past half-century. Survival for stage I testis cancer approaches 100% regardless of management strategy which is often dictated by other factors such as perceived morbidity. Advances in treatment have attempted to decrease morbidity and surveillance is thought to achieve this goal. METHODS: An English language literature search of MEDLINE from 1966 to December 2005 and CINAHL from 1982 to December 2005 was conducted using a broad search strategy. Comparative and descriptive original articles on outcomes of seminoma or NSGCT surveillance would be deemed eligible and review articles containing no original data were omitted. One hundred and thirty-eight articles were selected for formal review, during which a database was compiled that documented the first author, publication year, tumor histologic type, study purpose or topic(s), methodology, sample size, median follow-up, and relevant results. RESULTS: Most evidence for the efficacy of surveillance is from descriptive series or non-experimental comparative studies. Relapse occurs in approximately 28% and 17% of surveillance patients in NSGCT and seminoma, respectively, and cause-specific survival is approximately 98% and 100%, respectively. Compliance with surveillance ranges from poor to adequate, however there is no evidence that compliance impacts clinical outcome. Cost analyses have yielded inconsistent results when comparing treatment modalities. There is scant literature on quality of life and psychosocial issues and results are inconsistent. Active surveillance appears to be appropriate and perhaps optimal first line management of clinical stage I seminoma and non-seminomatous germ cell tumors. Further quantitative and qualitative research is warranted to deepen understanding of these issues that may impact treatment decision-making.

[Gaze-evoked amaurosis fugax]. / Blickinduzierte Amaurosis fugax.

Gaze-evoked amaurosis is a quite unique symptom. We present a 37-year-old patient with unilateral gaze-evoked amaurosis caused by an orbital tumor. Possible mechanisms include transient ischemia of the optic nerve and the retina or inhibition of the axonal impulses. While not common as a cause of amaurosis fugax, an orbital mass should be considered in the differential diagnosis of gaze-evoked atypical monocular amaurosis fugax.

Prospective trial of high-frequency oscillation in adults with acute respiratory distress syndrome.

OBJECTIVE: To evaluate the safety and efficacy of high-frequency oscillatory ventilation (HFOV) in adult patients with the acute respiratory distress syndrome (ARDS) and oxygenation failure. DESIGN: Prospective, clinical study. SETTING: Intensive care and burn units of two university teaching hospitals. PATIENTS: Twenty-four adults (10 females, 14 males, aged 48.5 +/- 15.2 yrs, Acute Physiology and Chronic Health Evaluation II score 21.5 +/- 6.9) with ARDS (lung injury score 3.4 +/- 0.6, Pao2/Fio2 98.8 +/- 39.0 mm Hg, and oxygenation index 32.5 +/- 19.6) who met one of the following criteria: Pao2 < or =65 mm Hg with Fio2 > or =0.6, or plateau pressure > or =35 cm H2O. INTERVENTIONS: HFOV was initiated in patients with ARDS after varying periods of conventional ventilation (CV). Mean airway pressure (Paw) was initially set 5 cm H2O greater than Paw during CV, and was subsequently titrated to maintain oxygen saturation between 88% and 93% and Fio2 < or =0.60. MEASUREMENTS AND MAIN RESULTS: Fio2, Paw, pressure amplitude of oscillation, frequency, blood pressure, heart rate, and arterial blood gases were monitored during the transition from CV to HFOV, and every 8 hrs thereafter for 72 hrs. In 16 patients who had pulmonary artery catheters in place, cardiac hemodynamics were recorded at the same time intervals. Throughout the HFOV trial, Paw was significantly higher than that applied during CV. Within 8 hrs of HFOV application, and for the duration of the trial, Fio2 and Paco2 were lower, and Pao2/Fio2 was higher than baseline values during CV. Significant changes in hemodynamic variables following HFOV initiation included an increase in pulmonary artery occlusion pressure (at 8 and 40 hrs) and central venous pressure (at 16 and 40 hrs), and a reduction in cardiac output throughout the course of the study. There were no significant changes in systemic or pulmonary pressure associated with initiation and maintenance of HFOV. Complications occurring during HFOV included pneumothorax in two patients and desiccation of secretions in one patient. Survival at 30 days was 33%, with survivors having been mechanically ventilated for fewer days before institution of HFOV compared with nonsurvivors (1.6 +/- 1.2 vs. 7.8 +/- 5.8 days; p =.001). CONCLUSIONS: These findings suggest that HFOV has beneficial effects on oxygenation and ventilation, and may be a safe and effective rescue therapy for patients with severe oxygenation failure. In addition, early institution of HFOV may be advantageous.

Agreement between alternative classifications of acute respiratory distress syndrome.

To examine the agreement between two classifications of acute respiratory distress syndrome (ARDS) that are used interchangeably in clinical practice and clinical research, we classified 118 patients taking part in a randomized trial with respect to the presence of ARDS using the North American-European Consensus Committee (NAECC) and the Lung Injury Severity Score (LISS) criteria. The incidence of ARDS using NAECC criteria was 55.1% (95% confidence interval, 46.1% to 64.1%), and using the LISS criteria 61.9% (95% confidence interval, 53.1% to 70.6%). The p value on the difference between these proportions was 0.07. Raw agreement, chance-corrected agreement (kappa), and chance-independent agreement (phi) on the study occurrence of ARDS using the two classifications were, respectively, 0.73 (95% CI, 0.65 to 0.81), 0.46 (95% CI, 0.32 to 0.61), and 0.63 (95% CI, 0.41 to 0.79). No single component of either index contributed to disagreement to an appreciably greater extent than other components. Baseline characteristics and outcomes were similar among patients who developed ARDS according to either classification. We conclude that NAECC and LISS classifications resulted in similar estimates of the incidence of ARDS in this clinical trial, though patients were frequently classified as having ARDS with only one model. These discordant classifications had no prognostic importance.

Interobserver variation in interpreting chest radiographs for the diagnosis of acute respiratory distress syndrome.

To measure the reliability of chest radiographic diagnosis of acute respiratory distress syndrome (ARDS) we conducted an observer agreement study in which two of eight intensivists and a radiologist, blinded to one another's interpretation, reviewed 778 radiographs from 99 critically ill patients. One intensivist and a radiologist participated in pilot training. Raters made a global rating of the presence of ARDS on the basis of diffuse bilateral infiltrates. We assessed interobserver agreement in a pairwise fashion. For rater pairings in which one rater had not participated in the consensus process we found moderate levels of raw (0.68 to 0.80), chance-corrected (kappa 0.38 to 0.55), and chance-independent (Phi 0. 53 to 0.75) agreement. The pair of raters who participated in consensus training achieved excellent to almost perfect raw (0.88 to 0.94), chance-corrected (kappa 0.72 to 0.88), and chance-independent (Phi 0.74 to 0.89) agreement. We conclude that intensivists without formal consensus training can achieve moderate levels of agreement. Consensus training is necessary to achieve the substantial or almost perfect levels of agreement optimal for the conduct of clinical trials.

Application of pharmacokinetics to electron-beam tomography of the abdomen.

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the pharmacokinetics of abdominal time-attenuation curves obtained at electron-beam tomography. MATERIALS AND METHODS: Computed tomographic enhancement data of the aorta, portal vein, vena cava, liver, spleen, and pancreas were obtained in 25 patients after injection of 50 mL of contrast medium. These data were used to calculate pharmacokinetic parameters such as half-lives, mean residence times, and areas under the curve with a computer program. RESULTS: Maximal enhancement was observed in the aorta 24 seconds +/- 5 (mean +/- standard deviation) after starting the injection of contrast medium (178 HU +/- 56), in the portal vein after 42 seconds +/- 14 (60 HU +/- 17), in the vena cava after 35 seconds +/- 7 (66 HU +/- 23), in the liver after 58 seconds +/- 15 (24 HU +/- 6), in the spleen after 35 seconds +/- 12 (42 HU +/- 16), and in the pancreas after 39 seconds +/- 15 (42 HU +/- 10). Half-lives of the last phase observed were 108 seconds +/- 123 in the aorta, 33 seconds +/- 30 in the portal vein, 49 seconds +/- 40 in the vena cava, 50 seconds +/- 54 in the liver, 62 seconds +/- 33 in the spleen, and 22 seconds +/- 27 in the pancreas. The computer program allowed for excellent fitting curves to the measured attenuation values and for subsequent calculation of pharmacokinetic parameters. New dosage regimens also could be simulated successfully. CONCLUSION: The pharmacokinetic parameters evaluated might be useful in the optimization of dosing and scanning parameters of the abdomen for ultrafast and helical CT.

Echo-enhanced Doppler sonography of focal nodular hyperplasia of the liver.

Lesions of focal nodular hyperplasia are hypervascular, benign focal liver lesions whose differentiation from other focal liver lesions is of significant clinical relevance. The purpose of this study was to investigate the echo-enhancing agent SHU 508A (Levovist) in the evaluation of focal nodular hyperplasia with Doppler sonography. We examined 49 patients with 71 lesions of focal nodular hyperplasia in the liver with gray scale and power Doppler sonography. In all patients Levovist was administered intravenously in a concentration of 300 to 400 mg galactose per milliliter. Visualization of the feeding vessels and the vascularity of the lesions were evaluated, and the resistive indices in the feeders and the hepatic arteries were assessed. In comparison with unenhanced power Doppler sonography, echo-enhanced power Doppler sonography yields a higher sensitivity in the detection of the feeding artery (97% versus 82%) in focal nodular hyperplasia and in the depiction of the radial vascular architecture in such lesions, especially those located in the left lobe of the liver. Lesions less than 3 cm in diameter do not consistently show a characteristic vascular architecture with echo-enhanced Doppler sonography. The resistive index of the tumor-feeding artery (mean, 0.51 +/- 0.09) is significantly (P < 0.0001) lower than that of the hepatic artery (mean, 0.65 +/- 0.06) and decreases as the size of the focal nodular hyperplasia increases. The administration of Levovist may improve the signal-to-noise ratio and thus visualization of the vascular architecture in focal nodular hyperplasia. Lesions located in the left lobe of the liver, which commonly are subject to disturbing motion artifacts in color Doppler sonography, will significantly benefit from the administration of Levovist. Echo-enhanced power Doppler sonography, however, is not capable of depicting a characteristic vascular pattern in small (< or = 3 cm) lesions of focal nodular hyperplasia that would guarantee a specific diagnosis.

Endoscopic removal of an intraorbital "tumor": a vital surprise.

We present the first case report of an endoscopic removal of a living worm, species Dirofilaria repens, from the orbital cavity. As of today, over 410 cases of Dirofilaria repens infections in man are recorded in world literature, six of which were localized in the orbital cavity. In Austria we know of four cases of an infection with this parasite, but none in the orbit. Dirofilaria repens is widespread only in the Old World, particularly in Southern and Eastern Europe, in Asia Minor, and in Central and Southern Asia. The highest prevalence of the disease is recorded in Italy (181 cases). In clinical practice, the infections have mostly been misdiagnosed as a neoplasia, usually benign but sometimes malignant. Under the assumption of an intraorbital tumor, the endoscopic transnasal revision of the orbital cavity was performed, as this approach promised to be least traumatic and best suited for the lesion, resulting in complete removal of the live worm. In unclear lesions in the head and neck, and infection with Dirofilaria repens should be considered as a differential diagnosis.

Topographic evaluation of lateral hypopharyngeal pouches using electron beam tomography.

BACKGROUND: To evaluate the exact topography of lateral hypopharyngeal pouches using electron beam tomography. METHODS: Seventeen patients, nine female, eight male, aged 28-72 years, who showed lateral hypopharyngeal pouches in the videofluorographic swallowing examination were studied using electron beam tomography. Upon swallowing a 20-ml bolus of water, the region of the thyrohyoid membrane was scanned 20 times per level. Scan parameters: single slice cine mode (exposure time 100 ms, slice thickness 3 mm, 620 mA, 130 KV). RESULTS: The lateral hypopharyngeal pouches appeared air-filled in the posterior aspect of the thyrohyoid membrane closely attached to the upper horn of the thyroid cartilage, just below the hyoid bone. CONCLUSIONS: With electron beam tomography it was possible to define the topographic location of the pouches more accurately, compared with the prior assumption of position.

Sonographic evaluation of focal nodular hyperplasias (FNH) of the liver with a transpulmonary galactose-based contrast agent (Levovist).

Focal nodular hyperplasias (FNH) are hypervascular, benign focal liver lesions. Differentiation of FNH from other focal liver lesions is of clinical importance. The purpose of this study was to examine the impact of a new, transpulmonary echo-enhancing agent SHU 508A (Levovist) and recent Doppler techniques in the sonographic evaluation of FNH. 43 patients with 61 focal nodular hyperplasias of the liver were examined with grey scale ultrasound and power Doppler ultrasound. Levovist, a galactose-air-microbubble suspension was administered intravenously in all patients, either by bolus injection (400 mg ml-1) or continuous pump-infusion (300 mg ml-1). Visualization of the feeding vessels and vascularity of the lesions were evaluated. The resistance indexes (RI) in the feeding vessel and the hepatic artery were assessed and compared with the diameters of the FNH. The mean diameter of FNH was 4.3 cm (+/- 1.0). Echo enhanced power Doppler ultrasound was superior to unenhanced power Doppler ultrasound in the detection of the feeding artery (85% vs. 98%) in FNH and depicted the internal vascular architecture more clearly, especially in lesions located in the left lobe of the liver. Lesions smaller than 3 cm did not show a characteristic vascular architecture with echo enhanced Doppler ultrasound. The resistance index of the feeding artery (mean: 0.51 +/- 0.08) is significantly (p < 0.0001) lower than that of the hepatic artery (mean 0.65 +/- 0.06) with a mean difference of -0.14 +/- 0.01 in the same patient. The RI of the feeding artery significantly decreased as the size of the FNH increased, whereas RI differences between the hepatic artery and the feeding artery increased with lesion size. Intravenous (i.v.) bolus injection of the contrast agent will depict the hypervascular nature of FNH more clearly than i.v. infusion, although the latter will significantly prolong the diagnostic window. In conclusion, i.v. infusion of Levovist improves the visualization of the feeding artery and the radiating vascular architecture in FNH located in the left lobe of the liver due to improved signal-to-noise ratio and results in more effective suppression of motion artefacts. Although echo enhanced Doppler ultrasound improves the detection of the low resistance arterial feeding vessel in small FNH, it will not, however, reveal a specific vascular pattern in these lesions.

Power Doppler imaging and evaluation of the resistive index in focal nodular hyperplasia of the liver.

Focal lesions of the liver represent a significant diagnostic problem for various imaging modalities. The aim of this study was to assess the value of power Doppler sonography versus conventional color Doppler imaging in the depiction of hypervascular focal nodular hyperplasia (FNH) of the liver and to investigate the resistive index (RI) in the lesions' feeding arteries. Eighteen histologically proved FNHs in 14 patients were evaluated by gray-scale ultrasound, conventional color Doppler, and power Doppler sonography. With conventional color Doppler, a feeding arterial vessel could be depicted in only 4/18 lesions and hypervascularization was detected in 6/18 lesions. Power Doppler was more sensitive in detecting feeding arteries (16/18) within hypervascular lesions (15/18). RI values in the feeding arteries (mean = 0.51) significantly differed from those in the main hepatic artery or its intraparenchymal branches (mean = 0.68) in the same patient. The mean RI-difference was 0.19, suggesting hemodynamically significant arteriovenous shunting. Power Doppler sonography significantly increases sensitivity in the diagnosis of focal nodular hyperplasia of the liver and reliably permits the distinction of these lesions from hepatocellular carcinomas.

Sonography of acute cholecystitis: comparison of color and power Doppler sonography in detecting a hypervascularized gallbladder wall.

OBJECTIVE: We evaluated the sensitivity and specificity of power Doppler sonography compared with conventional color Doppler sonography and gray-scale sonography in diagnosing patients with acute cholecystitis. SUBJECTS AND METHODS: Seventy-six patients with right upper quadrant pain and 72 healthy volunteers underwent gray-scale sonography, conventional color Doppler sonography, and power Doppler sonography of the gallbladder. The vascularity of the gallbladder wall was scored on a scale of 0 to +3. Histology revealed acute cholecystitis in 55 patients. Histologic specimens and clinical workups showed that the remaining 21 patients suffered from other diseases. RESULTS: Sensitive sonographic features such as the positive Murphy's sign (in 96% of patients with acute cholecystitis), calculi (95%), and a thickened gallbladder wall (73%) lacked specificity (71%, 38%, 67%, respectively) for diagnosing acute cholecystitis. In our study, the sensitivity of power Doppler sonography was 95% compared with 33% for color Doppler sonography in revealing a hypervascularized gallbladder wall. Power Doppler sonography revealed hyperemia within a nonthickened gallbladder wall in four patients with surgically proven acute cholecystitis. Specificity of power Doppler sonography was 86% compared with 95% for conventional color Doppler sonography. False-positive results with power Doppler sonography were caused by pancreatitis, duodenal ulcer, and gallbladder carcinoma. Interobserver variability seemed to play no significant role. No intramural hypervascularity was detected in the volunteer group. In four (4%) of 89 symptomatic patients we could not use power Doppler sonography because of the patients noncompliance. Mean values of the resistive index assessed within intramural vessels of the gallbladder showed no significant differences (p < .001) between patients with acute cholecystitis (0.73) and patients with other diseases (0.71). CONCLUSIONS: Although the sensitivity of power Doppler sonography in diagnosing acute cholecystitis was similar to that of gray-scale sonography, the specificity of power Doppler sonography was significantly higher, which may substantially improve diagnostic confidence. However, the high susceptibility of power Doppler sonography to motion artifacts makes appropriate adjustment of technical parameters much more relevant than with other sonographic imaging. The resistive index within intramural vessels has no clinical use in the diagnosis of acute cholecystitis.

[Functional studies of swallowing with electron beam computerized tomography]. / Funktionelle Schluckaktuntersuchungen mit der Elektronenstrahl-computertomographie.

Functional evaluation of swallowing disorders requires rapid imaging modalities. Videofluorography and cinematography are the gold standard, but they have their limitations: no transverse plane imaging is achieved and structural resolution for exact topographic analysis is limited. Three cases preselected by videofluorography were studied to evaluate whether electron beam tomography (EBT) permits more detailed dynamic imaging of swallowing disorders focusing on the mesonasopharyngeal segment, the hypopharynx and the upper esophageal sphincter (UES). Immediately after videofluorographic examination of the oropharyngeal deglutition, EBT is performed. The patient is in a supine position and while the patient swallows a 20 ml bolus of water or diluted iodine containing contrast agent, a sequence of 20 images per level is scanned. The levels, which are determined by using the scout view, are oriented parallel to the hard palate either at the level of the hard palate to image the mesonasopharyngeal segment or just above the hyoid bone to focus on the hypopharynx or at the location of the UES. The scan technique is a single-slice cinemode with a slice thickness of 3 mm (exposure time 100 ms, interscan delay 16 ms, 130 kV, 620 mA). The following structural interactions that we have so far been unable to image can be clearly demonstrated with EBT: (1) during normal swallowing, the mesonasopharyngeal segment is completely and symmetrically closed by the soft palate and Passavant's cushion; (2) lateral hypopharyngeal pouches can be located more precisely; and (3) disorders of the UES can be differentiated into functional or morphologically caused disorders (e.g., goiter or cervical osetophytes). Videofluorography and cinematography are still the gold standard in functional evaluation of swallowing disorders. However, EBT permits dynamic imaging of pharyngeal deglutition in a preselected transverse plane and can give useful additional information concerning functional anatomical changes in the pharynx during swallowing. Further clinical evaluation is needed.

Temperature dependent intermediate structures during the main phase transition of dimyristoyl phosphatidylcholine vesicles a combined iodine laser-temperature jump and time resolved cryo-electron microscopy study.

The kinetics of the main phase transition of dimyristoylphosphatidyl choline (DMPC) unilamellar vesicles were investigated in the time range from microseconds to seconds. Iodine laser-temperature jump (ILTJ) experiments showed three discrete relaxation phenomena. Time resolved cryo-electron microscopy (CEM) was applied to produce images of intermediate states typical for the relaxation times of lipid vesicles in the micro- to millisecond time window. A careful measurement of the rate of temperature decrease observed during the production of vitrified lamellae of aqueous samples on a copper grid was performed. The best conditions resulted in average rates of cooling of 3 x 10(4) K/s. By comparing the images from CEM of DMPC vesicle samples vitrified above, at, and below the phase transition temperature a structural model was designed, which explains the temperature jump relaxation times in the micro- to millisecond time range by the formation and disappearance of coexisting clusters of crystalline, intermediate, and fluid lipid areas inside the DMPC bilayers.