Postsurgical bile leaks: endoscopic obliteration of the transpapillary pressure gradient is enough

OBJECTIVES: Bile leaks are a well documented complication of biliary surgery, occurring more frequently with laparoscopic procedures. Endoscopic therapy with a long biliary endoprosthesis traversing the site of the leak is effective. We have evaluated the hypothesis that equalizing biliary and duodenal pressures with a short transpapillary stent is an equally effective therapy for bile leaks. METHODS: Thirty one consecutive patients presenting over a 52-month period with postsurgical bile leaks were evaluated. Patients had been treated with long endoprostheses (stents or nasobiliary tubes), sphincterotomy, or short transpapillary stents. The success, complication rate, need for additional therapy, and hospitalization time of each therapeutic approach were determined. RESULTS: Endoscopic therapy was successful in all 25 patients in whom a bile leak could be documented. The clinical success, need for radiological drainage, length of hospitalization, and incidence of pancreatitis were similar for all methods of treatment. CONCLUSIONS: These results confirm that endoscopic therapy is highly successful in the treatment of postoperative bile leaks and suggest that the mechanism of healing is the equalization of bile duct and duodenal pressures, allowing flow of bile into the duodenum. The endoscopic placement of short transpapillary stents without sphincterotomy is a temporary, effective, and technically simple method of pressure equalization. This should be considered as the primary therapy for most postoperative bile leaks.     

Mass transfer and thermodynamic effects in emulsion polymerisation

The course of emulsion polymerisation is shown to depend on the water-solubility of the monomers concerned. With insoluble monomers, the mass transfer rate of monomer to polymer particles can sometimes be exceeded by the polymerisation rate, and viscosity within the particles is appreciable throughout the course of the reaction. Thus, surfactant is adsorbed before monomer droplets disappear. With more soluble monomers, mass transfer rates of monomer are high and since the equilibrium concentration of polymer in particles is low the monomer droplets disappear early in the reaction. Consequently, water-insoluble monomers often conform to Smith-Ewart behaviour, whereas water-soluble monomers do not. With water-soluble monomers the final particle number is proportional to the cube of the initial surfactant concentration.     

Different elements of mini-helix 1 are required for human growth hormone or prolactin action via the prolactin receptor

Human growth hormone (hGH) and prolactin (hPRL) have a low sequence homology, but both bind and activate hPRL receptors. hGH also binds hGH receptors. hGH has 22 and 20 kDa forms; residues 32-46 have been deleted by alternative RNA splicing to create the smaller form. hGH requires F44 for activity through the hPRL receptor, but not for activity through the hGH receptor. The deletion of F44 from hGH has the same effect as removal of residues 32-46 (approximately 200-fold loss in activity), indicating the importance of F44 in hGH when activating the hPRL receptor. In contrast, when the homologous F50 is deleted from hPRL little or no activity is lost, indicating that this highly conserved phenylalanine is not required for the action of hPRL. Deletion of residues 41-52 (a non-conserved sequence homologous to residues 32-46 of hGH) reduced the activity of hPRL by >14 000-fold. This region is essential for the biological activity of hPRL. As these two proteins have evolved from a common ancestor, they have retained the requirement for this region but need different structural elements to activate hPRL receptors. Such diversity represents an opportunity to fine-tune hormone activity.     

A new method for defining and managing process alarms and for correcting process operation when an alarm occurs

A new mathematical treatment of alarms that considers them as multi-variable interactions between process variables has provided the first-ever method to calculate values for alarm limits. This has resulted in substantial reductions in false alarms and hence in alarm annunciation rates in field trials. It has also unified alarm management, process control and product quality control into a single mathematical framework so that operations improvement and hence economic benefits are obtained at the same time as increased process safety. Additionally, an algorithm has been developed that advises what changes should be made to Manipulable process variables to clear an alarm. The multi-variable Best Operating Zone at the heart of the method is derived from existing historical data using equation-free methods. It does not require a first-principles process model or an expensive series of process identification experiments. Integral with the method is a new format Process Operator Display that uses only existing variables to fully describe the multi-variable operating space. This combination of features makes it an affordable and maintainable solution for small plants and single items of equipment as well as for the largest plants. In many cases, it also provides the justification for the investments about to be made or already made in process historian systems. Field Trials have been and are being conducted at IneosChlor and Mallinckrodt Chemicals, both in the UK, of the new geometric process control (GPC) method for improving the quality of both process operations and product by providing Process Alarms and Alerts of much high quality than ever before. The paper describes the methods used, including a simple visual method for Alarm Rationalisation that quickly delivers large sets of Consistent Alarm Limits, and the extension to full Alert Management with highlights from the Field Trials to indicate the overall effectiveness of the method in practice.     

Comparative psychometric analysis of vector and isochrone cardiac activation maps

Isochronal cardiac activation maps can be constructed from local activation times associated with spatial locations, and are frequently used to study cardiac arrhythmias. Cardiac velocity vector mapping has been proposed as an alternative method to study cardiac activation in both clinical and research environments. Velocity vectors inherently contain more information than scalar measures of latency, but it is unknown how vector maps and isochronal maps compare when they are used to identify patterns and features associated with arrhythmias. In order to quantitatively compare these two visualization methods, eight cardiologists were asked to complete forced-choice tasks in which they selected ablation sites based on synthetic vector or isochronal maps. Maps varied in arrhythmia complexity, number of vectors or activation times included, and errors in magnitude or angle for maps of velocity vectors. Quantitative comparison was achieved by using psychometric functions to characterize the learning curve and the total number of measurements needed in order to choose a correct ablation site. For simple arrhythmias, performance with vector maps was superior to isochronal maps. Subjects required fewer measurements, and learned more rapidly by studying vector maps. For more complex arrhythmias, there was no significant difference in performance between vector and isochronal maps. However, arrhythmia features were clearer with vector maps, even though this clarity did not necessarily change the ablation site choice. When errors were added to vector maps, performance was satisfactory for angle errors < 55 degrees, and speed errors did not affect performance.     

Measurement of neutron fluence spectra up to 150 MeV using a stacked scintillator neutron spectrometer

A stacked scintillator neutron spectrometer (S3N) consisting of three slabs of liquid organic scintillator is described. A pulsed beam providing a broad spectrum of neutron energies is used to determine the detection efficiency of the spectrometer as a function of incident neutron energy and to measure the pulse height response matrix of the system. Neutron spectra can then be determined for beams with any kind of time structure by unfolding pulse height spectra measured by the S3N. Examples of fluence spectrum measurements in the energy range 20-150 MeV are presented.