Dennis L. Coleman

Streaming potential investigations: Polymer thin films

Abstract Streaming potential evaluations were carried out on a wide variety of biopolymer and synthetic polymer thin films supported on glass microscope slides. The film-forming and streaming evaluation techniques are sufficiently accurate to provide reproducible results between different investigators. Films evaluated to date include various silanes, albumins, agarose, and synthetic polymers based on hydroxyethyl methacryle (HEMA), n -butyl methacrylate ( n -BMA), and methylacrmethylate (MMA). The effect of negative and positive charge incorporation upon the streaming potential and thus the ζ potential was studied via incorporation of methacrylic acid (MAA) and both HC1 and CH 3 C1 salts of dimethylaminoethyl methacrylate (DMAEMA) into the neutral polymer chains of HEMA, n -BMA, and MMA via copolymerization. Thin films of polystyrene, polydimethyl siloxane, polyvinyl chloride, and avcothane were also evaluated successfully.

Clinical Evaluation of a Raman Scattering Multiple Gas Analyzer for the Operating Room

A Raman spectrometer multiple gas analyzer was used to monitor inspired and expired concentrations of oxygen (O2), nitrogen (N2), carbon dioxide (CO2), nitrous oxide (N2O), halothane, and isoflurane in 10 patients. The Raman spectrometer and a dedicated mass spectrometer were connected to each patient to provide a comparison of the two instruments. Results show that readings from the Raman spectrometer are within 0.62 vol% of known gas standards for O2, N2, N2O; within 0.03 vol% for CO2; and within 0.04 vol% for halothane, enflurane and isoflurane. Clinical results show that Raman spectrometer readings are within 1.36 vol% of the mass spectrometer readings for O2, N2, N2O; within 0.01 vol% for CO2; and within 0.22 vol% for halothane and isoflurane. The clinical and laboratory results indicate the Raman spectrometer monitors airway gases and vapors as accurately as a dedicated mass spectrometer.

Dedicated monitoring of anesthetic and respiratory gases By Raman scattering

The monitoring of respiratory and anesthetic gases in the operating room is important for patient safety. This study measured the accuracy and response time of a multiplegas monitoring instrument that uses Raman light scattering. Measurements of oxygen, carbon dioxide, nitrogen, nitrous oxide, halothane, enflurane, and isoflurane concentrations were compared with a gas mixer standard and with measurements made with an infrared anesthetic agent analyzer. Correlation coefficients were all greater than 0.999, and probable errors were less than 0.43 vol% for the gases and less than 0.03 vol% for the volatile anesthetics. Response time was 67 ms with a sample flow rate of 150 ml/min. There was some signal overlap between nitrogen and nitrous oxide and between the volatile anesthetic agents. Such overlap can be compensated for by linear matrix analysis. The Raman instrument promises a monitoring capability equivalent to the mass spectrometer and should prove attractive for the monitoring of respiratory and anesthetic gases in the operating room.

Polymer Properties Associated with Calcification of Cardiovascular Devices

Nucleation and growth of calcium phosphate crystals on blood pumps designed to assist or replace the natural heart is a limiting factor in the long-term survival of experimental animals. This phenomenon, first reported by Olsen et al. [24] in 1975, is an acknowledged problem in all cardiovascular implant centers with routine animal survival times greater than 100 days[8]. The exact cause of the deposition of calcium phosphate, crystallization, and growth is not known, but several factors have been identified as important participants in the process. These factors will be discussed in some detail below.

Commercial anesthetic-respiratory gas monitor utilizing Raman spectroscopy

A commercial gas monitor which utilizes Raman Spectroscopy has been developed to monitor anesthetic and respiratory gases in the hospital operating room. The instrument measures all molecular gases administered by the anesthesiologist in real time with fast response of breath waveform. These gases include carbon dioxide, nitrous oxide, oxygen, nitrogen and various volatile halogenated organic anesthetics, e.g. halothane, isoflurane, enflurane, sevoflurane and desflurane. The key feature of this instrument which allows it to produce adequate Raman signals with a low cost argon ion laser is measuring these gases inside the laser resonant cavity.

Surfaces With Minimal Or Selective Protein Adsorption Interactions As Model Biomedical Polymers

The amount, type, conformation and orientation of proteins that adsorb at an interface during the first minutes of blood exposure are felt to dominate the blood compatibility response of that surface. This study attempts to clarify the role protein adsorption plays in blood-materials interactions by utilising model polymer systems which show minimal protein adsorption at physiological ionic strength and pH. One of these surfaces is then derivatised by various means to allow for selective protein interactions. Bloodmaterials investigations can then be studied as a function of protein interactions with this substrate.