Energy Balances for Axisymmetric Gravity Currents in Homogeneous and Linearly Stratified Ambients

We analyse the exchange of energy for an axisymmetric gravity current, released instantaneously from a lock, propagating over a horizontal boundary at high Reynolds number. The study is relevant to flow in either a wedge or a full circular geometry. Attention is focused on effects due to a linear stratification in the ambient. The investigation uses both a one-layer shallow-water model and Navier–Stokes finite-difference simulations. There is fair agreement between these two approaches for the energy changes of the dense fluid (the current). The stratification enhances the accumulation of potential energy in the ambient and reduces the energy decay (dissipation) of the two-fluid system. The total energy of the axisymmetric current decays considerably faster with distance of propagation than for the two-dimensional counterpart

On right conjugacy closed loops of twice prime order

The right conjugacy closed loops of order 2p, where p is an odd prime, are classified up to isomorphism.Comment: Clarified definitions, added some remarks and a tabl

Block-Transitive Designs in Affine Spaces

This paper deals with block-transitive $t$-$(v,k,\lambda)$ designs in affine spaces for large $t$, with a focus on the important index $\lambda=1$ case. We prove that there are no non-trivial 5-$(v,k,1)$ designs admitting a block-transitive group of automorphisms that is of affine type. Moreover, we show that the corresponding non-existence result holds for 4-$(v,k,1)$ designs, except possibly when the group is one-dimensional affine. Our approach involves a consideration of the finite 2-homogeneous affine permutation groups.Comment: 10 pages; to appear in: "Designs, Codes and Cryptography

Axial pumps for propulsion systems

The development of axial flow hydrogen pumps is examined. The design features and the performance data obtained during the course of the development programs are discussed. The problems created by the pump characteristics are analyzed. Graphs of four stage pump performance for various turbine blade configurations are developed. The characteristics and performance of a variety of pumps are included

Liquid rocket engine axial-flow turbopumps

The axial pump is considered in terms of the total turbopump assembly. Stage hydrodynamic design, pump rotor assembly, pump materials for liquid hydrogen applications, and safety factors as utilized in state of the art pumps are among the topics discussed. Axial pump applications are included

Is There an “Acquired Idiopathic Head-Shaking Nystagmus”?—A Discussion of Mechanisms and Clinical Implications Based on a Case Report

Background: Head-shaking nystagmus (HSN) occurs in both peripheral and central vestibular disorders. In most cases, HSN can be attributed to an asymmetric peripheral vestibular input or a structural lesion mostly in the cerebellum affecting the central velocity storage mechanism. An isolated HSN is very rare. Case Presentation: We report on a young female patient with the clinical picture of recurrent episodes of vertigo, which were induced by fast head movements and were accompanied by a severe right-beating HSN with a long time constant of 60 s. There was no other clinical and instrument-based evidence of peripheral vestibular dysfunction (including video head impulse test, caloric test, vestibular-evoked myogenic potentials) or indication of a structural lesion in the nodulus, uvula or pontomedullary brainstem on fine-slice magnetic resonance imaging. She had no previous history of migraine, hearing deficits, or other focal neurological symptoms. Diagnostic criteria for vestibular paroxysmia, vestibular migraine, benign peripheral paroxysmal vertigo, or any other known vestibular disorders were not fulfilled. Chart review in the database of the German Center for Vertigo and Balance Disorders indicated eight additional patients with a similar clinical phenotype between 2018 and 2022. Conclusion: We propose a clinical entity called acquired idiopathic head shaking nystagmus (aiHSN) as a rare cause of episodic vertigo induced by fast head movements. Nystagmus characteristics suggest a subtle functional pathology of the central velocity storage mechanism in the nodulus and uvula, which is exacerbated during symptomatic episodes

On p-stability in groups and fusion systems

The aim of this paper is to generalise the notion of p-stability (p is an odd prime) in finite group theory to fusion systems. We first compare the different definitions of p-stability for groups and examine properties of p -stability concerning subgroups and factor groups. Motivated by Glauberman's theorem, we study the question of how Qd(p) is involved in finite simple groups. We show that with a single exception a simple group involving Qd(p) has a subgroup isomorphic to either Qd(p) or a central extension of Qd(p) by a cyclic group of order p. Then we define p-stability for fusion systems and characterise some of its properties. We prove a fusion theoretic version of Thompson's maximal subgroup theorem. We introduce the notion of section p-stability both for groups and fusion systems and prove a version of Glauberman's theorem to fusion systems. We also examine relationship between solubility and p -stability for fusion systems and determine the simple groups whose fusion systems are Qd(p)-free

Direct visualization of G-quadruplexes in DNA using atomic force microscopy

The formation of G-quadruplexes in G-rich regions of DNA is believed to affect DNA transcription and replication. However, it is currently unclear how this formation occurs in the presence of a complementary strand. We have used atomic force microscopy (AFM) to image stable RNA/DNA hybrid loops generated by transcription of the plasmid pPH600, which contains a 604-bp fragment of the murine immunoglobulin Sγ3 switch region. We show that the non-RNA-containing portion folds into G-quadruplexes, consistent with computational predictions. We also show that hybrid formation prevents further transcription from occurring, implying a regulatory role. After in vitro transcription, almost all (93%) of the plasmids had an asymmetric loop, a large asymmetric blob or a spur-like projection at the appropriate position on the DNA contour. The loops disappeared following treatment of the transcribed plasmid with RNase H, which removes mRNA hybridized with the template strand. Replacement of K+ in the transcription buffer with either Na+ or Li+ caused a reduction in the percentage of plasmids containing loops, blobs or spurs, consistent with the known effects of monovalent cations on G-quadruplex stability. The minimal sample preparation required for AFM imaging has permitted direct observation of the structural changes resulting from G-quadruplex formation

Performance of J33 turbojet engine with shaft-power extraction III : turbine performance

The performance of the turbine component of a J33 turbojet engine was determined over a range of turbine speeds from 8000 to 11,500 rpm.Turbine-inlet temperature was varied from the minimum required to drive the compressor to a maximum of approximately 2000 degrees R at each of several intermediate turbine speeds. Data are presented that show the horsepower developed by the turbine per pound of gas flow. The relation between turbine-inlet stagnation pressure, turbine-outlet stagnation pressure, and turbine-outlet static pressure was established. The turbine-weight-flow parameter varied from 39.2 to 43.6. The maximum turbine efficiency measured was 0.86 at a pressure ratio of 3.5 and a ratio of blade speed to theoretical nozzle velocity of 0.39. A generalized performance map of the turbine-horsepower parameter plotted against the turbine-speed parameter indicated that the best turbine efficiency is obtained when the turbine power is 10 percent greater than the compressor horsepower. The variation of efficiency with the ratio of blade speed to nozzle velocity indicated that the turbine operates at a speed above that for maximum efficiency when the engine is operated normally with the 19-inch-diameter jet nozzle