Prompt acceleration of ions by oblique turbulent shocks in solar flares

Solar flares often accelerate ions and electrons to relativistic energies. The details of the acceleration process are not well understood, but until recently the main trend was to divide the acceleration process into two phases. During the first phase elctrons and ions are heated and accelerated up to several hundreds of keV simultaneously with the energy release. These mildly relativistic electrons interact with the ambient plasma and magnetic fields and generate hard X-ray and radio radiation. The second phase, usually delayed from the first by several minutes, is responsible for accelerating ions and electrons to relativistic energies. Relativistic electrons and ions interact with the solar atmosphere or escape from the Sun and generate gamma ray continuum, gamma ray line emission, neutron emission or are detected in space by spacecraft. In several flares the second phase is coincident with the start of a type 2 radio burst that is believed to be the signature of a shock wave. Observations from the Solar Maximum Mission spacecraft have shown, for the first time, that several flares accelerate particles to all energies nearly simultaneously. These results posed a new theoretical problem: How fast are shocks and magnetohydrodynamic turbulence formed and how quickly can they accelerate ions to 50 MeV in the lower corona? This problem is discussed

Energetic ion acceleration at collisionless shocks

An example is presented from a test particle simulation designed to study ion acceleration at oblique turbulent shocks. For conditions appropriate at interplanetary shocks near 1 AU, it is found that a shock with theta sub B n = 60 deg is capable of producing an energy spectrum extending from 10 keV to approx. 1 MeV in approx 1 hour. In this case total energy gains result primarily from several separate episodes of shock drift acceleration, each of which occurs when particles are scattered back to the shock by magnetic fluctuations in the shock vicinity

Electrical characteristics of a free-burning direct-current argon arc operating between 90 and 563 kilowatts with two types of cathodes

The electrical characteristics of a high-power, long-lived, free-burning dc argon arc are presented. Empirical formulas relating voltage to current, electrode separation, and operating pressure are given for two types of cathodes: a typical point tip cathode and a cathode with a 1.27-cm-(0.5-in.-) diameter crater in the tip. Power was varied from 90 to 563 kW. A discussion of the cathode with the crater tip is given

Summary on tau Leptonic Branching Ratios and Universality

The large samples of tau decays available from CLEO and the four LEP experiment have resulted in new, precise measurements of the leptonic branching ratios of the $\tau$. The experimental techniques to obtain these results are reviewed with special emphasis on the DELPHI measurement. World averages are found to be Be = (17.81 +/- 0.06) % and Bmu = (17.36 +/- 0.06) %. These results are consistent with universality in the charged current couplings to a precision of about 0.25 %. The branching ratio measurements can also be used to constrain the "low energy parameter" eta. It is shown that the sensitivity to eta depends on details of the momentum acceptance for muon identification in the different experiments. Assuming universality in the couplings, the estimate eta = 0.012 +/- 0.024 is obtained.Comment: 10 pages, LaTeX, including 9 figures, uses epsf and espcrc2. Invited talk at the Fifth Intl. Workshop on Tau Lepton Physics, 14-17 September 1998, Santander (Spain

Convergence Rates for Newton’s Method at Singular Points

If Newton’s method is employed to find a root of a map from a Banach space into itself and the derivative is singular at that root, the convergence of the Newton iterates to the root is linear rather than quadratic. In this paper we give a detailed analysis of the linear convergence rates for several types of singular problems. For some of these problems we describe modifications of Newton’s method which will restore quadratic convergence

What do we know about succession in family businesses? Mapping current knowledge and unexplored territory

We review studies on succession in family businesses that have been done since Handler’s (1994) seminal literature review on the topic in an effort to synthesize existing research and outline paths for future studies. We offer three contributions. First, we select succession studies that adhere to established methodological standards. Second, we review these studies based on the perspective that succession is a process comprising five stages across three levels of analysis. Finally, we outline current gaps in our knowledge and ask researchers to adopt a more holistic approach when studying succession

THE IMPACT OF POSTTRAUMATIC STRESS DISORDER ON PERIPHERAL VASCULAR FUNCTION

The physiological manifestations of posttraumatic stress disorder (PTSD) have been associated with an increase in risk of cardiovascular disease (CVD) independent of negative lifestyle factors. Peripheral vascular dysfunction may be a mechanism by which PTSD increases CVD risk via increases in oxidative stress, inflammation, and/or sympathetic nervous system activity. PURPOSE: This study sought to examine peripheral vascular function in those with PTSD compared to age-matched controls. METHODS: Eight individuals with PTSD (5 women, 3 men; age 22 ± 2 years), and sixteen healthy controls (CON; 10 women, 6 men, 23 ± 2 years), participated in the study. Leg vascular function was assessed via passive leg movement (PLM) technique and evaluated with Doppler ultrasonography. PLM-induced increases in leg blood flow were quantified as peak change in blood flow from baseline (ΔPeak LBF) and blood flow area under the curve (LBF AUC). RESULTS: Significant differences in leg vascular function were revealed between groups. The PTSD group reported significantly lower ΔPeak LBF (PTSD: 294.16 ± 54.16; CON: 594.78 ± 73.70 ml∙min-1; p = 0.01) and LBF AUC (PTSD: 57.23 ± 24.37; CON: 169.92 ± 29.84 ml; p = 0.02) when compared to the CON group. CONCLUSION: This study revealed that lower limb vascular function is impaired in individuals with PTSD when compared to healthy counterparts.https://scholarscompass.vcu.edu/gradposters/1043/thumbnail.jp

Voyager 1 and 2 measurements of radial and latitudinal cosmic ray gradients during 1981 - 1984

The cosmic ray radial gradient was determined during 1981-84 using data from very similar detectors onboard spacecraft Voyagers 1 and 2 (radial separation approx. 6 AU, heliolatitude separation approx. 25 deg.) and from the Earth-orbiting satellite IMP 8. The principal result is that the radial gradient over this period decreased at the rate approx. 2.0%/AU between 1 and 16 AU and approx. 0.6%/AU between approx. 16 and 22 AU

Evaluating Pedestrial Compaction Variation & Soil Organic C Content

Over time, playing fields are monitored by overall appearance. However, pedestrian compaction is not evenly distributed throughout the entire surface