Pilot study of pathophysiology of constipation among community diabetics

We aimed to compare gastrointestinal transit and defecatory function in a random sample of people with or without diabetes mellitus in a US community who reported constipation or laxative use. In this pilot study we measured: gastric, small bowel, and colonic transit by scintigraphy; vector manometry of anal sphincters at rest and during squeeze; defecatory dynamics by balloon expulsion test; and scintigraphic measurement of anorectal angle at rest and during defecation. Autonomic function tests were performed in diabetics. Diabetics with constipation had a higher prevalence of abnormal evacuation or prolonged colonic transit during the first 24 hr than controls (P = 0.07): three had prolonged 24-hr colonic transit, and three abnormal evacuation. Among constipated controls, only one had anismus. Overall, diabetics had slower colonic transit during the first 24 hr than nondiabetics (P < 0.05). Community diabetics who experience constipation or use laxatives have a greater prevalence of delayed 24-hr colonic transit or evacuatory dysfunction than community controls.     

Offset-free combined neural network/switching control for nonlinearservomechanisms with DSP-based implementation

In this paper, we present a combined neural network/switching controller which is shown to provide offset-free regulation and control in the presence of disturbances. The controller is applicable to nonlinear servomechanisms of the type commonly encountered in motion control. In the paper, the properties of the controller are discussed and the implementation of the overall control system using a microcomputer host with a digital signal processor (DSP) accelerator is described. The paper also includes the results of real-time experiments in applying the proposed controller for position control of a nonlinear servomechanism which provides experimental verification of the effectiveness of the proposed method     

Quality assurance of serial tomotherapy for head and neck patient treatments

PURPOSE: A commercial serial tomotherapy intensity-modulated radiation therapy (IMRT) treatment planning (Peacock, NOMOS Corp., Sewickley, PA) and delivery system is in clinical use. The dose distributions are highly conformal, with large dose gradients often surrounding critical structures, and require accurate localization and dose delivery. Accelerator and patient-specific quality assurance (QA) procedures have been developed that address the localization, normalization, and delivery of the IMRT dose distributions. METHODS AND MATERIALS: The dose distribution delivered by serial tomotherapy is highly sensitive to the accuracy of the longitudinal couch motion. There is also an unknown sensitivity of the dose distribution on the dynamic mutlileaf collimator alignment. QA procedures were implemented that assess these geometric parameters. Evaluations of patient positioning accuracy and stability were conducted by exposing portal films before (single exposure) and after (single or double exposure) treatments. The films were acquired with sequential exposures using the largest available fixed multileaf portal (3.36 x 20 cm2). Comparison was made against digitally reconstructed radiographs generated using independent software and appropriate beam geometries. The delivered dose was verified using homogeneous cubic phantoms. Radiographic film was used to determine the localization accuracy of the delivered isodose distributions, and ionization chambers and thermoluminescent dosimetry (TLD) chips were used to verify absolute dose at selected points. Ionization chamber measurements were confined to the target dose regions and TLD measurements were obtained throughout the irradiated volumes. Because many more TLD measurements were made, a statistical evaluation of the measured-to-calculated dose ratio was possible. RESULTS: The accelerator QA techniques provided adequate monitoring of the geometric patient movement and dynamic multileaf collimator alignment and positional stability. The absolute delivered dose as measured with the ionization chamber varied from 0.94 to 0.98. Based on these measurements, the delivered monitor units for both subsequent QA measurements and patient treatments were adjusted by the ratio of measured to calculated dose. TLD measurements showed agreement, on average, with the ionization chamber measurements. The distribution of TLD measurements in the high-dose regions indicated that measured doses agreed within 4.2% standard deviation of the calculated doses. In the low-dose regions, the measured doses were on average 5% greater than the calculated doses, due to a lack of leakage dose in the dose calculation algorithm. CONCLUSIONS: The QA system provided adequate determination of the geometric and dosimetric quantities involved in the use of IMRT for the head and neck. Ionization chamber and TLD measurements provided accurate determination of the absolute delivered dose throughout target volumes and critical structures, and radiographic film yielded precise dose distribution localization verification. Portal film acquisition and subsequent portal film analysis using 3.36 x 20 cm2 portals proved useful in the evaluation of patient immobilization quality. Adequate bony landmarks were imaged when carefully selected portals were used.     

Cellular-structure glass formed with phlogopite-type mica powders and carbonate compounds

Cellular-structure glass or foamed glass has been fabricated from mixtures of recycled colorless soda-lime waste glass powders and three separate different foaming agents by a simple sintering process. One of the mixtures consisted of glass powders and a locally produced mica powder of the phlogopite-type, which act as a foaming agent as well as a component of the glass-mica composite material. The other mixtures consisted of glass powders and a carbonate compound, now with calcium carbonate and one with sodium carbonate. The fabricated cellular-structure of the glass-mica composite material is found to have superior mechanical and thermal properties when compared with the cellular-structure glass formed with the carbonate compounds. The mechanisms of the formation of the cellular-structure by the two systems are discussed.     

Composite autonomic scoring scale for laboratory quantification of generalized autonomic failure

An autonomic reflex screen, which consisted of a quantitative sudomotor axon reflex test, orthostatic blood pressure and heart rate response to tilt, heart rate response to deep breathing, the Valsalva ratio, and beat-to-beat blood pressure measurements during phases II and IV of the Valsalva maneuver, tilt, and deep breathing, was used to develop a 10-point composite autonomic scoring scale of autonomic function. The scheme allots 4 points for adrenergic and 3 points each for sudomotor and cardiovagal failure. Each score is normalized for the compounding effects of age and sex. Patients with a score of 3 or less on the composite autonomic scoring scale have only mild autonomic failure, those with scores of 7 to 10 have severe failure, and those with scores between these two ranges have moderate autonomic failure. The sensitivity and specificity of the method were assessed by evaluating the composite autonomic scoring scale in four groups of patients with known degrees of autonomic failure: 18 with multisystem atrophy, 20 with autonomic neuropathy, 20 with Parkinson's disease, and 20 with peripheral neuropathy but no autonomic symptoms. The composite scores (means +/- SD) for these four groups, respectively, were as follows: 8.5 +/- 1.3, 8.6 +/- 1.2, 1.5 +/- 1.1, and 1.7 +/- 1.3. Patients with symptomatic autonomic failure had scores of 5 or more, those without symptomatic autonomic failure had scores of 4 or less, and no overlap existed in these groups. Thus, autonomic laboratory tests should be useful in grading the degree of autonomic failure.     

On the Pressure Distribution in Uncharged Membranes During Osmotic Plow

Experiments indicated that adsorptive forces lower the potential energy of water inside uncharged cellulose acetate membranes. As a result it is postulated that the steady-state pressure distribution during osmosis is affected. In particular, a sudden rise in pressure should occur across the water-membrane interface. Thus, in this region, water may flow against a pressure gradient.     

The fabrication of light-emitting devices from hot-pressed ZnSe powders

A hot-pressing process was developed to synthesize fine ZnSe powders into compacts with high bulk density. The hot-pressed ZnSe powder compacts after an annealing treatment in the Zn-Al alloy melt were readily processed into light-emitting devices based on a metal-semiconductor (M-S) device structure. The fabricated devices are found to emit light in the orange region of the visible spectrum and have a room temperature quantum efficiency of the order of 10^–6 photons/electron in the reverse direction. The photoluminescence and electroluminescence characteristics of the hot-pressed ZnSe powder compacts are also found to be very similar to those observed in single crystal material.