Determinations of nonprotein nitrogen content of cheese whey.

Nonprotein nitrogen in pooled sweet (Cheddar and Dagano) and acid (cottage) wheys was estimated by currently proposed dialysis and chemical precipitation methods. Kjeldahl nitrogen analyses of (a) membrane retentates after water dialysis, and (b) 12% trichloroacetic acid plus .2% phosphotungstic acid filtrates indicated that nonprotein nitrogen values vary significantly with the method of sample preparation. Membrane porosity influence nonprotein nitrogen values for molecular weight cut-offs of 3500, 6000 to 8000 and 12,000 to 14,000. Dialyzable nitrogen values with all membranes were lower than 12% trichloroacetic acid soluble nitrogen for both wheys and higher than the 12% trichloroacetic acid + .2% phosphotungstic acid soluble nitrogen for all but the 3500 molecular weight cut-off membrane. The dialyzable nonprotein nitrogen fraction was heterogeneous but more that 80% was less than 3500 in molecular weight.     

Electrophysiology of atrial fibrillation and its prevention by coronary sinus pacing

OBJECTIVES: Prehospital providers are often unable to obtain intravenous (i.v.) access in cardiac arrest victims. While several drugs can be administered via the endotracheal (ET) route, serum drug levels are lower than those obtained with the i.v. route. The authors hypothesized that a 90-degree torso tilt after ET drug administration would increase drug levels. METHODS: A randomized, prospective, unblinded laboratory trial was conducted. Twenty-three mixed-breed domestic swine (20-25 kg) were sedated, anesthetized, instrumented, shocked into cardiac arrest, and randomized into three groups. Lidocaine was administered either i.v. (1.5 mg/kg), traditional ET (4.5 mg/kg), or ET followed by a 5-second 90-degree upright torso tilt (4.5 mg/kg). While standard CPR was performed, lidocaine levels were obtained at 0.5, 1, 2, 3, 4, and 5 minutes after administration. Repeated-measures ANOVA was used for data analysis (alpha = 0.05). RESULTS: Experimental ET compared with traditional ET administration produced significantly higher levels at all time points except 0.5 minutes. Comparing experimental ET with i.v. administration yielded significantly higher levels for the i.v. route at 0.5 and 1 minute and for the experimental ET route at 4 and 5 minutes. i.v. lidocaine administration resulted in significantly higher levels at 0.5, 1, and 2 minutes when compared with traditional ET administration. CONCLUSIONS: Endotracheal instillation of lidocaine followed by a 90-degree torso tilt resulted in better drug absorption, as evidenced by higher serum lidocaine levels, than did traditional recumbent ET delivery at all but the earliest time point and produced more sustained lidocaine levels than i.v. administration at 4 and 5 minutes. ET drug delivery followed by a 5-second 90-degree torso tilt and the mechanisms for this enhanced absorption warrant further investigation.     

Coronary sinus pacing prevents induction of atrial fibrillation

BACKGROUND: Atrial fibrillation (AF) is due to reentry, and its incidence has been shown to decrease after dual-site atrial or biatrial pacing. We investigated whether a simpler pacing approach via the distal coronary sinus (CSd) could eliminate AF inducibility by high right atrial (HRA) extrastimuli (APDs). We based our hypothesis on our previous observation that AF inducibility by HRA APDs was associated with conduction delays to the posterior triangle of Koch, whereas AF was never induced with CSd APDs, which were associated with minimal intra-atrial conduction delays. METHODS AND RESULTS: Programmed electrical stimulation was performed from the high right atrium and CSd, and bipolar recordings were obtained from the high right atrium, His bundle, posterior triangle of Koch, and coronary sinus. In 13 patients (age, 44+/-18 years), AF was reproducibly induced with a critically timed HRA APD (220+/-22 ms) delivered during HRA pacing. AF was not induced in any of the patients when HRA APDs were delivered during CSd pacing at the same critical coupling intervals. Coronary sinus APDs delivered during HRA pacing also were not associated with AF induction. The APD coupling interval measured at the posterior triangle of Koch during CSd pacing was significantly prolonged compared with the one measured during HRA pacing and AF induction (381+/-58 versus 263+/-37 ms; P<.0001). CONCLUSIONS: We propose that CSd pacing suppresses the propensity of HRA APDs to induce AF by limiting their prematurity at the posterior triangle of Koch and not allowing local conduction delay and local reentry to occur.     

The Design and Testing of a Self-Actuated Shut down System for the Protection of Liquid Metal Fast Breeder Reactors (LMFBRS)

Most nuclear reactors are shut down automatically upon the receipt of an external electrical signal which actuates the shutdown device. The design and testing of a simple and reliable Self-Actuated Shutdown System (SASS) for the protection of Liquid Metal Fast Breeder Reactors (LMFBRs) is described here. Self-actuation refers to the capability of the system to be triggered by abnormal changes in reactor variables at the location of the device which can be in the reactor core itself. A ferromagnetic Curie temperature permanent magnet holding device has been selected for the design of the Self-Actuated Shutdown System in order to enhance the safety of liquid metal cooled fast reactors (LMFBRs). The self-actuated, self-contained device operates such that accident conditions, resulting in increased coolant temperature or neutron flux reduce the magnetic holding force suspending a neutron absorber above the core by raising the temperature of the trigger mechanism above the Curie point. Neutron absorber material is then inserted into the core, under gravity, terminating the accident. Two possible design variations of the selected concept are presented. The proposed designs derive the magnetic holding force from an Alnico V permanent magnet which drives the magnetic holding flux through the parting plane of a carbon steel magnetic circuit. Magnetic and thermal-hydraulic analyses have been performed which show the feasibility of the concept with respect to response time, holding force, and coolability. A series of experiments have been performed which demonstrate proof of principle of the selected Curie point magnetic hold device.     

Method of determining nanoparticle core weight

Polymer-coated metal or metal oxide nanoparticles have a variety of uses in industry, biological research, and medicine. Characterization of nanoparticles often includes determination of the dimensions of the electron-dense core by transmission electron microscopy (TEM), with the weight of the core determined from core volume and core density. However, TEM is labor intensive, has a long turnaround time, and uses equipment that is sometimes not readily available. Here we present an alternative method for determining the weight of nanoparticle cores termed the viscosity/light scattering method, which uses (i) measurements of viscosity over a wide concentration range to obtain the partial specific volume, (ii) measurements of particle diameter by light scattering, to obtain the volume of an individual particle, and (iii) the concentration of nanoparticles (w/v). We have applied this method to determine the weights of nanoparticle cores (iron of amino-CLIO and ferritin), the weights of globular proteins (molecular weight of IgG and albumin), and the weight of polystyrene microspheres. The viscosity/light scattering method is nondestructive of the sample and can be performed with a variety of materials on a routine basis.     

Sprint start instrumentation

A prototype instrument has been developed to measure the forces generated on the starting blocks and the speed of a sprinter at the start of a sprint event. The starting block forces can be resolved into horizontal and vertical components for each foot, or the various combinations of these four forces can be calculated and displayed along with the resultant angle. The speed of the sprinter is measured by means of a Doppler microwave technique (radar gun). Both static and dynamic tests have been used to calibrate the force transducers and to verify their functional bandwidth. The speed measurement technique has been validated by four independent procedures: measurement of a constant velocity object; measurement of an object undergoing constant acceleration; determination of distance travelled by an athlete; and comparison with high-speed cinematography. Both the force and speed profiles can be displayed immediately on the screen of a microcomputer for feedback to the coach and athlete during training sessions     

Molecular MR Imaging Probes

Magnetic resonance imaging (MRI) has been successfully applied to many of the applications of molecular imaging. This review discusses by example some of the advances in areas such as multimodality MR-optical agents, receptor imaging, apoptosis imaging, angiogenesis imaging, noninvasive cell tracking, and imaging of MR marker genes.     

Atmospheric Noise Study Program

Replacement of noise grade maps by a computer program will give more accurate results than are now obtained. The means for accomplishing the change are discussed.