Vortex Rings Generated by a Shrouded Hartmann-Sprenger Tube

The pulsed flow emitted from a shrouded Hartmann-Sprenger tube was sampled with high-frequency pressure transducers and with laser particle imaging velocimetry, and found to consist of a train of vortices. Thrust and mass flow were also monitored using a thrust plate and orifice, respectively. The tube and shroud lengths were altered to give four different operating frequencies. From the data, the radius, velocity, and circulation of the vortex rings was obtained. Each frequency corresponded to a different length to diameter ratio of the pulse of air leaving the driver shroud. Two of the frequencies had length to diameter ratios below the formation number, and two above. The formation number is the value of length to diameter ratio below which the pulse converts to a vortex ring only, and above which the pulse becomes a vortex ring plus a trailing jet. A modified version of the slug model of vortex ring formation was used to compare the observations with calculated values. Because the flow exit area is an annulus, vorticity is shed at both the inner and outer edge of the jet. This results in a reduced circulation compared with the value calculated from slug theory accounting only for the outer edge. If the value of circulation obtained from laser particle imaging velocimetry is used in the slug model calculation of vortex ring velocity, the agreement is quite good. The vortex ring radius, which does not depend on the circulation, agrees well with predictions from the slug model

An Archaeological Survey of Randleman and Howard Mills Reservoirs

A miscellaneous report by the Research Laboratories of Archaeology, University of North Carolina at Chapel Hill. These reports discuss the findings of archaeological survey, testing, and excavations undertaken by the RLA between 1973 and 1985

1974 Excavations Within the New Hope Reservoir

A miscellaneous report by the Research Laboratories of Archaeology, University of North Carolina at Chapel Hill. These reports discuss the findings of archaeological survey, testing, and excavations undertaken by the RLA between 1973 and 1985

Policy Influence and Reelection in the European Parliament

Introduction: In this paper, we undertake two challenges: measuring political influence and using influence to explain reelection. First, we develop a new measure of policy leadership in the European Parliament (EP), by which we mean leadership by lawmakers in particular policy domains. Second, we investigate the predictive power of this new indicator by considering its ability to explain individual MEPs’ reelection. In other words, we ask if policy leaders are more likely to be reelected, controlling for relevant confounding factors, such as formal party and legislative leadership, seniority, and the electoral performance of MEPs’ national parties

Sobre La Naturaleza Del Lenguaje

En nuestro medio está bastante arraigada la idea de que todo lenguaje es comunicación, y, a la inversa, hay quien supone que toda comunicación animal o humana es lenguaje. Se oye hablar, por ejemplo, de 'la lengua escrita, el lenguaje de los gestos, el lenguaje de las abejas, de las loras, o de este animal o del otro'. Pero, más que comunicación, podríamos definir el lenguaje como un sistema de simbolización que media, en una forma sumamente compleja, entre el universo del significado y el universo del sonido

EL ESPAÑOL DE COSTA RICA: ESTUDIO FONOLÓGICO GENERATlVO

En nuestra discusión sobre variantes fonológicos desviados en el español de costa Rica, hemos aceptado las matrices de abrientes, núcleos y cerrantes que se encuentran en Saporta y Contreras (1962). Aunque podría hablarse de pequeños reajustes de ciertos detalles, cualquier reformulación por nuestra parte agregaría poco nuevo

International study into the use of intermittent hormone therapy in the treatment of carcinoma of the prostate : A meta-analysis of 1446 patients

OBJECTIVE: To review pooled phase II data to identify features of different regimens of intermittent hormone therapy (IHT), developed to reduce the morbidity of treating metastatic prostate cancer, and which carries a theoretical advantage of delaying the onset of androgen-independent prostate cancer, (AIPC) that are associated with success, highlighting features which require exploration with prospective trials to establish the best strategies for using this treatment. METHODS: Individual data were collated on 1446 patients with adequate information, from 10 phase II studies with >50 cases, identified through Pubmed. RESULTS: Univariate and multivariate Cox proportional hazard models were developed to predict treatment success with a high degree of statistical success. The prostate-specific antigen (PSA) nadir, the PSA threshold to restart treatment, and medication type and duration, were important predictors of outcome. CONCLUSIONS: The duration of biochemical remission after a period of HT is a durable early indicator of how rapidly AIPC and death will occur, and will make a useful endpoint in future trials to investigate the best ways to use IHT based on the important treatment cycling variables described above. Patients spent a mean of 39% of the time off treatment. The initial PSA level and PSA nadir allow the identification of patients with prostate cancer in whom it might be possible to avoid radical therapy.Peer reviewe