Performance analysis of three-phase inverters controlled bysynchronous delta-modulation systems

Synchronous delta-modulation systems are used to control resonant voltage link inverters, where switching has to be synchronized with the zero crossings of the link voltage. This paper shows that output current harmonic distortion and average switching frequency of such systems can be calculated analytically in spite of the quasistochastic behavior of the modulators output. Under the assumption of constant link frequency and large ratio of link to output frequency, results are derived for three-phase sigma-delta modulation, space-vector based sigma-delta modulation, and current-regulated delta modulation. The results hold for any shape of the inverter input voltage (including DC). The output current harmonic distortion of resonant link inverters is compared with conventional hard switching PWM inverters     

Efficacy of carbohydrate sources for milk production by cows fed diets based on alfalfa silage

The effectiveness of three carbohydrate sources, high-moisture ear corn (HMEC), cracked shelled corn (CSC), and a 50:50 mixture of HMEC plus dried citrus pulp (DCP), fed with or without supplemental rumen-undegraded protein as expeller soybean meal (ESBM), was assessed in 48 multiparous dairy cows. All diets contained (dry mater [DM] basis) 50% alfalfa silage, 10% ryegrass silage, 28% NDF, and one of six concentrates: A) 38% HMEC; B) 38% CSC; C) 19% DCP plus 19% HMEC; D) 27% HMEC plus 12% ESBM; E) 27% CSC plus 12% ESBM; or F) 13% DCP, 13% HMEC, and 12% ESBM. Diets A, B, and C averaged 19% crude protein, of which 53% was nonprotein nitrogen (NPN), and diets D, E, and F averaged 22% crude protein, of which 40% was NPN. Cows were fed a high-energy covariate diet for 2 wk, blocked into eight groups of six, based on covariate protein yield, then randomly assigned to diets that were fed for 12 wk. Feeding ESBM increased DM intake, yields of milk, fat-corrected milk, fat, protein, SNF, and milk and blood urea concentration and decreased weight loss. There were no production differences between HMEC and CSC. However, DM intake, yields of milk, fat-corrected milk, fat, protein, lactose, SNF, and milk SNF content all were lower on the diets containing DCP versus HMEC and CSC. A 6 x 6 Latin square trial conducted at the same time with six ruminally cannulated cows showed similar effects of diet on DM intake and milk production. Ruminal ammonia was elevated by ESBM but not ruminal total amino acids and branched-chain volatile fatty acids. Ruminal propionate was highest on HMEC diets and lowest on DCP diets; acetate, butyrate and acetate-to-propionate ratio were lowest on HMEC diets and highest on DCP diets. These results indicated that, compared to HMEC and CSC, feeding the pectin-rich carbohydrate source DCP altered ruminal fermentation but depressed intake and milk production in lactating cows.     

Structurally related peptide agonist, partial agonist, and antagonist occupy a similar binding pocket within the cholecystokinin receptor. Rapid analysis using fluorescent photoaffinity labeling probes and capillary electrophoresis

The molecular basis of ligand binding to receptors provides important insights for drug development. Here, we explore domains of the cholecystokinin (CCK) receptor that are critical for ligand binding, using a novel series of fluorescent photolabile probes, receptor proteolysis, and rapid high resolution separation of peptide fragments by capillary electrophoresis. Each probe incorporated the same fluorophore and a photolabile p-benzoylphenylalanine at the amino terminus of the pharmacophoric domain (residue 24 of CCK-33) of CCK analogues representing full agonist, partial agonist, and antagonist of this receptor. Each was used to label the CCK receptor expressed on Chinese hamster ovary-CCKR cells, with the labeled domain then released by cyanogen bromide cleavage. Capillary electrophoresis with laser-induced fluorescence detection achieved an on-capillary mass sensitivity of 1.6 attomoles (10(-18) mol), with an excellent signal-to-noise ratio. Each of the biologically divergent, but structurally similar probes saturably and specifically labeled the same receptor domain, consistent with conservation of "docking" determinants. This had an apparent mass of 2.9 kDa, most consistent with the first extracellular loop domain. An additional probe having its site of covalent attachment in a different region of the probe (residue 29 of CCK-33) labeled a distinct receptor fragment with differential migration on capillary electrophoresis (third extracellular loop). Identification of the specific receptor residue(s) covalently linked to the amino-terminal probes must await further fragmentation and sequence analysis.     

Pseudomutagenesis. The persistent increase in the level of cellular variability induced by radiation and some other agents

Electron microscopic investigation of capillary endothelium cells in myocardium of irradiated rats revealed an unusual effect of persistent increase of probability of cell damage, similar in many relations to that described earlier for various unicellular species. New effect, unlike those traditionally studied, is characterised by non-stochastic nature, large number of the involved cells, reveals itself even after faint influences, and can be induced as well by agents other than radiation. The question is put on the probable commonness between these changes and the pseudomutagenesis which has the similar phenomenology.     

A prospective randomized comparison of epidural infusion of fentanyl and intravenous administration of morphine by patient-controlled analgesia after radical retropubic prostatectomy

In a prospective, randomized study, continuous infusion of epidural fentanyl citrate (group E) was compared with patient-controlled intravenously administered morphine sulfate (group P) for analgesia in 66 men after radical retropubic prostatectomy. Although both methods provided satisfactory analgesia, the mean comfort level scores were lower (that is, greater comfort) in group E than in group P at all observation times. The difference in mean resting comfort level scores between groups E and P was statistically significant (P < or = 0.05) at 9 of the 11 observation times. In addition, significant differences in comfort level scores were noted at 8 of the 11 observation times during deep breathing, 5 of 11 during coughing, and 3 of 9 during ambulation. Maximal and minimal comfort level scores recorded by each patient during the course of the study were significantly lower (that is, less pain) in group E than in group P for all four categories of activity. The percentage of patients who reported no pain was significantly higher in group E than in group P at 9 of 11 observation times during resting and 5 of 11 observation times during deep breathing. No significant differences were noted in side effect profiles or duration of hospital stay. In summary, when two effective methods of analgesia used after radical retropubic prostatectomy were compared prospectively, patients who received epidural infusion of fentanyl were more comfortable than those with patient-controlled intravenous administration of morphine, as evidenced by lower mean, maximal, and minimal comfort level scores and a greater proportion of patients with complete relief of pain.     

The yielding, plastic flow, and fracture behavior of ultra-high molecular weight polyethylene used in total joint replacements

The yielding, plastic flow, and fracture behavior of UHMWPE plays an important role in wear and failure mechanisms of total joint replacement components. The primary objective of this study was to compare the yielding, plastic flow, and fracture behavior of two implantable grades of UHMWPE (GUR 1120 vs 4150 HP). The first part of this work explored the hypothesis that up to the polymer yield point, the monotonic loading behavior of UHMWPE displays similar true stress strain behavior in tension and compression. Uniaxial tension and compression tests were conducted to compare the equivalent true stress vs strain response of UHMWPE up to 0.12 true strain. During monotonic loading, the equivalent true stress strain behavior was similar in tension and compression up to the yield point. However, investigation of the unloading behavior and permanent plastic deformations showed that classical deviatoric rate independent plasticity theory may dramatically overpredict the permanent strains in UHMWPE. A secondary goal of this study was to determine the ultimate true stress and strain for UHMWPE and to characterize the fracture surfaces after failure. Using a fracture mechanics approach, the critical flaw sizes were used in combination with the true ultimate stresses to predict the fracture toughness of the two resins. A custom video-based strain measurement system was developed and validated to characterize the true stress-strain behavior up to failure and to verify the accuracy of the incompressibility assumption in calculating the true stress-strains up to failure. In a detailed uncertainty analysis, theoretical expressions were derived for the relative uncertainty in digital video-based estimates of nominal strain, true strain, homogeneous stress, and true stress. Although the yielding behavior of the two UHMWPE resins was similar, the hardening and plastic flow behavior clearly discriminated between the GUR 1120 and 4150 HP. A statistically significant difference between the fracture toughness of the two resins was also evident. The long-term goal of this research is to provide detailed true stress strain data for UHMWPE under uniaxial tension and compression for future numerical simulations and comparison with more complex multiaxial loading conditions.     

The efficacy of oral appliances in the treatment of persistent sleep apnea after uvulopalatopharyngoplasty

Twenty-four patients who failed uvulopalatopharyngoplasty (UPPP) for obstructive sleep apnea (OSA) had an adjustable oral (Herbst) appliance made to treat the persistent apnea. Six patients discontinued the device prior to sleep evaluation. Eighteen patients had polysomnographic evaluations at baseline, post-UPPP, and with the Herbst appliance in place. The apnea-hypopnea index baseline (AHI) and arterial oxygen saturation (SaO2) nadir were 42.3+/-6.1 and 83.6+/-1.8%, respectively. There was no significant change in either parameter with surgery. With the oral appliance, the AHI fell to 15.3+/-4.4 (p < or = 0.01) and the SaO2 nadir increased to 87.9+/-1.2% (p < or = 0.05). Ten of the patients had control of the OSA with the Herbst appliance with a fall in the AHI to < 10. There were, in addition, two partial responders as defined by an AHI of <20 and a >50% fall in AHI compared with baseline and post-UPPP values. All but one of the responders and partial responders had complete resolution of subjective symptoms of daytime sleepiness with the appliance. An adjustable oral appliance appears to be an effective mode of therapy to control OSA after an unsuccessful UPPP.