Partial cavity instabilities

This paper reviews some of the literature on partial cavity instabilities on single hydrofoils and then summarizes the striking differences in the appearance and behavior of partial cavities on swept foils (as opposed to two-dimensional, unswept foils) as rcently highlighted by de Lange et al. (1994) and Laberteaux and Ceccio (1998). These demonstrate the importance of the spanwise evolution of the re-entrant jet, and the consequences for the characteristics of the cavity closure flow. It is suggested in this paper that several variants of this evolution can be seen in the photographs of cavitation on single hydrofoils foils and on propellers. What is common to many of these variants is that, the spanwise evolution of the cavity and the re-entrant jet can give rise to conditions at some particular spanwise location(s) which initiate partial cavity instability. In this paper we present information on an instability that was observed to occur on a cavitating propeller of modern US Navy design. Detailed photographic examinations show that the instability oscillations involve spanwise development of a re-entrant jet and behavior similar to that of the partial cavity oscillations previously observed on two-dimensional foils

Surge Instability on a Cavitating Propeller

This study details experiments investigating a previously unrecognized surge instability on a cavitating propeller in a water tunnel. The surge instability is explored through visual observation of the cavitation on the propeller blades and in the tip vortices. Similarities between the instability and previously documented cavitation phenomena are noted. Measurements of the radiated pressure are obtained, and the acoustic signature of the instability is identified. The magnitudes of the fluctuating pressures are very large, presumably capable of producing severe hull vibration on a ship. The origins of this instability are explored through separate investigation of the cavitation dynamics and the response of the water tunnel to volumetric displacement in the working section. Experiments are conducted to quantify the dynamics of the propeller cavitation. Finally, a model is developed for the complete system, incorporating both the cavitation and facility dynamics. The model predicts active system dynamics (linked to the mass flow gain factor familiar in the context of pump dynamics) and therefore potentially unstable behavior for two distinct frequency ranges, one of which appears to be responsible for the instability

Photometric and spectroscopic gamma-ray observations of solar transient phenomena using long duration balloons

A program currently in progress to conduct extended duration spectroscopic and photometric observation of solar X-ray phenomena from balloons is described. High photometric sensitivity to weak hard X-ray bursts is attained using a 600 sq cm array of phoswich scintillators. High spectral resolution for stronger bursts is available from an array of planar germanium detectors. These instruments are carried in a novel balloon gondola dssigned for the 15 to 20 day float durations available through using conventional zero pressure balloons in the radiation controlled (RACOON) mode

A high-resolution gamma-ray and hard X-ray spectrometer for solar flare observations in Max 1991

A long duration balloon flight instrument for Max 1991 designed to study the acceleration of greater than 10 MeV ions and greater than 15 keV electrons in solar flares through high resolution spectroscopy of the gamma ray lines and hard X-ray and gamma ray continuum is described. The instrument, HIREGS, consists of an array of high-purity, n-type coaxial germanium detectors (HPGe) cooled to less than 90 K and surrounded by a bismuth germanate (BGO) anticoincidence shield. It will cover the energy range 15 keV to 20 MeV with keV spectral resolution, sufficient for accurate measurement of all parameters of the expected gamma ray lines with the exception of the neutron capture deuterium line. Electrical segmentation of the HPGe detector into a thin front segment and a thick rear segment, together with pulse-shape discrimination, provides optimal dynamic range and signal-to-background characteristics for flare measurements. Neutrons and gamma rays up to approximately 0.1 to 1 GeV can be detected and identified with the combination of the HPGe detectors and rear BGO shield. The HIREGS is planned for long duration balloon flights (LDBF) for solar flare studies during Max 1991. The two exploratory LDBFs carried out at mid-latitudes in 1987 to 1988 are described, and the LDBFs in Antarctica, which could in principle provide 24 hour/day solar coverage and very long flight durations (20 to 30 days) because of minimal ballast requirements are discussed

Beliefs around luck : confirming the empirical conceptualization of beliefs around luck and the development of the Darke and Freedman beliefs around luck scale

The current study developed a multi-dimensional measure of beliefs around luck. Two studies introduced the Darke and Freedman beliefs around luck scale where the scale showed a consistent 4 component model (beliefs in luck, rejection of luck, being lucky, and being unlucky) across two samples (n = 250; n = 145). The scales also show adequate reliability statistics and validity by ways of comparison with other measures of beliefs around luck, peer and family ratings and expected associations with measures of personality, individual difference and well-being variables

IL1RL1 Gene Variants and Nasopharyngeal IL1RL-a Levels Are Associated with Severe RSV Bronchiolitis: A Multicenter Cohort Study

Targets for intervention are required for respiratory syncytial virus (RSV) bronchiolitis, a common disease during infancy for which no effective treatment exists. Clinical and genetic studies indicate that IL1RL1 plays an important role in the development and exacerbations of asthma. Human IL1RL1 encodes three isoforms, including soluble IL1RL1-a, that can influence IL33 signalling by modifying inflammatory responses to epithelial damage. We hypothesized that IL1RL1 gene variants and soluble IL1RL1-a are associated with severe RSV bronchiolitis.We studied the association between RSV and 3 selected IL1RL1 single-nucleotide polymorphisms rs1921622, rs11685480 or rs1420101 in 81 ventilated and 384 non-ventilated children under 1 year of age hospitalized with primary RSV bronchiolitis in comparison to 930 healthy controls. Severe RSV infection was defined by need for mechanical ventilation. Furthermore, we examined soluble IL1RL1-a concentration in nasopharyngeal aspirates from children hospitalized with primary RSV bronchiolitis. An association between SNP rs1921622 and disease severity was found at the allele and genotype level (p = 0.011 and p = 0.040, respectively). In hospitalized non-ventilated patients, RSV bronchiolitis was not associated with IL1RL1 genotypes. Median concentrations of soluble IL1RL1-a in nasopharyngeal aspirates were >20-fold higher in ventilated infants when compared to non-ventilated infants with RSV (median [and quartiles] 9,357 [936-15,528] pg/ml vs. 405 [112-1,193] pg/ml respectively; p<0.001).We found a genetic link between rs1921622 IL1RL1 polymorphism and disease severity in RSV bronchiolitis. The potential biological role of IL1RL1 in the pathogenesis of severe RSV bronchiolitis was further supported by high local concentrations of IL1RL1 in children with most severe disease. We speculate that IL1RL1a modifies epithelial damage mediated inflammatory responses during RSV bronchiolitis and thus may serve as a novel target for intervention to control disease severity

Appraisal patterns of envy and related emotions

Envy is a frustrating emotion that arises from upward social comparison. Two studies investigated the appraisals that distinguish benign envy (aimed at improving one’s own situation) from malicious envy (aimed at pulling down the superior other). Study 1 found that appraisals of deservingness and control potential differentiated both types of envy. We manipulated these appraisals in Study 2 and found that while both did not influence the intensity of envy, they did determine the type of envy that resulted. The more a situation was appraised as undeserved, the more participants experienced malicious envy. Benign envy was experienced more when the situation was not undeserved, and the most when the situation was appraised as both deserved and controllable. The current research also clarifies how the types of envy differ from the related emotions admiration and resentment

The synthetic bacterial lipopeptide Pam3CSK4 modulates respiratory syncytial virus infection independent of TLR activation

Respiratory syncytial virus (RSV) is an important cause of acute respiratory disease in infants, immunocompromised subjects and the elderly. However, it is unclear why most primary RSV infections are associated with relatively mild symptoms, whereas some result in severe lower respiratory tract infections and bronchiolitis. Since RSV hospitalization has been associated with respiratory bacterial co-infections, we have tested if bacterial Toll-like receptor (TLR) agonists influence RSVA2- GFP infection in human primary cells or cell lines. The synthetic bacterial lipopeptide Pam3-Cys-Ser-Lys4 (Pam3CSK4), the prototype ligand for the heterodimeric TLR1/TLR2 complex, enhanced RSV infection in primary epithelial, myeloid and lymphoid cells. Surprisingly, enhancement was optimal when lipopeptides and virus were added simultaneously, whereas addition of Pam3CSK4 immediately after infection had no effect. We have identified two structurally related lipopeptides without TLR-signaling capacity that also modulate RSV infection, whereas Pam3CSK4-reminiscent TLR1/2 agonists did not, and conclude that modulation of infection is independent of TLR activation. A similar TLR-independent enhancement of infection could also be demonstrated for wild-type RSV strains, and for HIV-1, measles virus and human metapneumovirus. We show that the effect of Pam3CSK4 is primarily mediated by enhanced binding of RSV to its target cells. The Npalmitoylated cystein