The Rocketdyne Multifunction Tester. Part 2: Operation of a Radial Magnetic Bearing as an Excitation Source

The operation of the magnetic bearing used as an excitation source in the Rocketdyne Multifunction Tester is described. The tester is scheduled for operation during the summer of 1990. The magnetic bearing can be used in two control modes: (1) open loop mode, in which the magnetic bearing operates as a force actuator; and (2) closed loop mode, in which the magnetic bearing provides shaft support. Either control mode can be used to excite the shaft; however, response of the shaft in the two control modes is different due to the alteration of the eigenvalues by closed loop mode operation. A rotordynamic model is developed to predict the frequency response of the tester due to excitation in either control mode. Closed loop mode excitation is shown to be similar to the excitation produced by a rotating eccentricity in a conventional bearing. Predicted frequency response of the tester in the two control modes is compared, and the maximum response is shown to be the same for the two control modes when synchronous unbalance loading is not considered. The analysis shows that the response of this tester is adequate for the extraction of rotordynamic stiffness, damping, and inertia coefficients over a wide range of test article stiffnesses

Suppression of Subsynchronous Vibration in the SSME HPFTP

Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP) hot-fire dynamic data evaluation and rotordynamic analysis both confirm that two of the most significant turbopump attributes in determining susceptibility to subsynchronous vibration are impeller interstage seal configuration and rotor sideload resulting from turbine turnaround duct configuration and hot gas manifold. Recent hot-fire testing has provided promising indications that the incorporation of roughened damping seals at the impeller interstages may further increase the stability margin of this machine. A summary of the analysis which led to the conclusion that roughened seals would enhance the stability margin is presented along with a correlation of the analysis with recent test data

Association between depressive symptom clusters and food attentional bias

Background The mechanisms underlying the depression-obesity relationship are unclear. Food attentional bias (FAB) represents one candidate mechanism that has not been examined. We evaluated the hypothesis that greater depressive symptoms are associated with increased FAB. Method Participants were 89 normal weight or overweight adults (mean age = 21.2 ± 4.0 years, 53% female, 33% non-white, mean body mass index in kg/m2 = 21.9 ± 1.8 for normal weight; 27.2 ± 1.5 for overweight). Total, somatic, and cognitive-affective depressive symptom scores were computed from the Patient Health Questionnaire-8 (PHQ-8). FAB scores were calculated using reaction times (RT) and eye-tracking (ET) direction and duration measures for a food visual probe task. Age, gender, race/ethnicity, and body fat percent were covariates. Results Only PHQ-8 somatic symptoms were positively associated with RT-measured FAB (β = 0.23, p = .04). The relationship between somatic symptoms and ET direction (β = 0.18, p = .17) and duration (β = 0.23, p = .08) FAB indices were of similar magnitude but were not significant. Somatic symptoms accounted for 5% of the variance in RT-measured FAB. PHQ-8 total and cognitive-affective symptoms were unrelated to all FAB indices (ps ≥ 0.09). Conclusions Only greater somatic symptoms of depression were linked to food attentional bias as measured using reaction time. Well-powered prospective studies should examine whether this bias replicates, particularly for eye-tracking measures, and whether it partially mediates the depression-to-obesity relationship

Alterations in vasodilator-stimulated phosphoprotein (VASP) phosphorylation: associations with asthmatic phenotype, airway inflammation and β\u3csub\u3e2\u3c/sub\u3e-agonist use

Background Vasodilator-stimulated phosphoprotein (VASP) mediates focal adhesion, actin filament binding and polymerization in a variety of cells, thereby inhibiting cell movement. Phosphorylation of VASP via cAMP and cGMP dependent protein kinases releases this brake on cell motility. Thus, phosphorylation of VASP may be necessary for epithelial cell repair of damage from allergen-induced inflammation. Two hypotheses were examined: (1) injury from segmental allergen challenge increases VASP phosphorylation in airway epithelium in asthmatic but not nonasthmatic normal subjects, (2) regular in vivo β2-agonist use increases VASP phosphorylation in asthmatic epithelium, altering cell adhesion. Methods Bronchial epithelium was obtained from asthmatic and non-asthmatic normal subjects before and after segmental allergen challenge, and after regularly inhaled albuterol, in three separate protocols. VASP phosphorylation was examined in Western blots of epithelial samples. DNA was obtained for β2-adrenergic receptor haplotype determination. Results Although VASP phosphorylation increased, it was not significantly greater after allergen challenge in asthmatics or normals. However, VASP phosphorylation in epithelium of nonasthmatic normal subjects was double that observed in asthmatic subjects, both at baseline and after challenge. Regularly inhaled albuterol significantly increased VASP phosphorylation in asthmatic subjects in both unchallenged and antigen challenged lung segment epithelium. There was also a significant increase in epithelial cells in the bronchoalveolar lavage of the unchallenged lung segment after regular inhalation of albuterol but not of placebo. The haplotypes of the β2-adrenergic receptor did not appear to associate with increased or decreased phosphorylation of VASP. Conclusion Decreased VASP phosphorylation was observed in epithelial cells of asthmatics compared to nonasthmatic normals, despite response to β-agonist. The decreased phosphorylation does not appear to be associated with a particular β2-adrenergic receptor haplotype. The observed decrease in VASP phosphorylation suggests greater inhibition of actin reorganization which is necessary for altering attachment and migration required during epithelial repair

Four dimensional Lie symmetry algebras and fourth order ordinary differential equations

Realizations of four dimensional Lie algebras as vector fields in the plane are explicitly constructed. Fourth order ordinary differential equations which admit such Lie symmetry algebras are derived. The route to their integration is described.Comment: 12 page

An Obstruction to Quantization of the Sphere

In the standard example of strict deformation quantization of the symplectic sphere $S^2$, the set of allowed values of the quantization parameter $\hbar$ is not connected; indeed, it is almost discrete. Li recently constructed a class of examples (including $S^2$) in which $\hbar$ can take any value in an interval, but these examples are badly behaved. Here, I identify a natural additional axiom for strict deformation quantization and prove that it implies that the parameter set for quantizing $S^2$ is never connected.Comment: 23 page. v2: changed sign conventio

Quantum teardrops

Algebras of functions on quantum weighted projective spaces are introduced, and the structure of quantum weighted projective lines or quantum teardrops are described in detail. In particular the presentation of the coordinate algebra of the quantum teardrop in terms of generators and relations and classification of irreducible *-representations are derived. The algebras are then analysed from the point of view of Hopf-Galois theory or the theory of quantum principal bundles. Fredholm modules and associated traces are constructed. C*-algebras of continuous functions on quantum weighted projective lines are described and their K-groups computed.Comment: 18 page

High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect of PRNP genotype and age

Following a severe outbreak of clinical scrapie in 2006–2007, a large dairy goat herd was culled and 200 animals were selected for post-mortem examinations in order to ascertain the prevalence of infection, the effect of age, breed and PRNP genotype on the susceptibility to scrapie, the tissue distribution of diseaseassociated PrP (PrP$^{\rm d}$), and the comparative efficiency of different diagnostic methods. As determined by immunohistochemical (IHC) examinations with Bar224 PrP antibody, the prevalence of preclinical infection was very high (72/200; 36.0%), with most infected animals being positive for PrP$^{\rm d}$ in lymphoreticular system (LRS) tissues (68/72; 94.4%) compared to those that were positive in brain samples (38/72; 52.8%). The retropharyngeal lymph node and the palatine tonsil showed the highest frequency of PrP$^{\rm d}$ accumulation (87.3% and 84.5%, respectively), while the recto-anal mucosa-associated lymphoid tissue (RAMALT) was positive in only 30 (41.7%) of the infected goats. However, the efficiency of rectal and palatine tonsil biopsies taken shortly before necropsy was similar. The probability of brain and RAMALT being positive directly correlated with the spread of PrP$^{\rm d}$ within the LRS. The prevalence of infection was influenced by PRNP genetics at codon 142 and by the age of the goats: methionine carriers older than 60 months showed a much lower prevalence of infection (12/78; 15.4%) than those younger than 60 months (20/42; 47.6%); these last showed prevalence values similar to isoleucine homozygotes of any age (40/80; 50.0%). Two of seven goats with definite signs of scrapie were negative for PrP$^{\rm d}$ in brain but positive in LRS tissues, and one goat showed biochemical and IHC features of PrP$^{\rm d}$ different from all other infected goats. The results of this study have implications for surveillance and control policies for scrapie in goats