A heater made from graphite composite material for potential deicing application

A surface heater was developed using a graphite fiber-epoxy composite as the heating element. This heater can be thin, highly electrically and thermally conductive, and can conform to an irregular surface. Therefore it may be used in an aircraft's thermal deicing system to quickly and uniformly heat the aircraft surface. One-ply of unidirectional graphite fiber-epoxy composite was laminated between two plies of fiber glass-epoxy composite, with nickel foil contacting the end portions of the composite and partly exposed beyond the composites for electrical contact. The model heater used brominated P-100 fibers from Amoco. The fiber's electrical resistivity, thermal conductivity and density were 50 micro ohms per centimeter, 270 W/m-K and 2.30 gm/cubic cm, respectively. The electricity was found to penetrate through the composite in the transverse direction to make an acceptably low foil-composite contact resistance. When conducting current, the heater temperature increase reached 50 percent of the steady state value within 20 sec. There was no overheating at the ends of the heater provided there was no water corrosion. If the foil-composite bonding failed during storage, liquid water exposure was found to oxidize the foil. Such bonding failure may be avoided if perforated nickel foil is used, so that the composite plies can bond to each other through the perforated holes and therefore lock the foil in place

Escape, capture, and levitation of matter in Eddington outbursts

Context: An impulsive increase in luminosity by one half or more of the Eddington value will lead to ejection of all optically thin plasma from Keplerian orbits around the radiating star, if gravity is Newtonian and the Poynting-Robertson drag is neglected. Radiation drag may bring some particles down to the stellar surface. On the other hand, general relativistic calculations show that gravity may be balanced by a sufficiently intense radiation field at a certain distance from the star. Aims: We investigate the motion of test particles around highly luminous stars to determine conditions under which plasma may be ejected from the system. Results: In Einstein's gravity, if the outburst is close to the Eddington luminosity, all test particles orbiting outside an "escape sphere" will be ejected from the system, while all others will be captured from their orbits onto the surface of another sphere, which is well above the stellar surface, and may even be outside the escape sphere, depending on the value of luminosity. Radiation drag will bring all the captured particles to rest on this "Eddington capture sphere," where they will remain suspended in an equilibrium state as long as the local flux of radiation does not change and remains at the effective Eddington value.Comment: 6 pages, 6 figures. To be published in Astronomy and Astrophysic

Oscillations of the Eddington Capture Sphere

We present a toy model of mildly super-Eddington, optically thin accretion onto a compact star in the Schwarzschild metric, which predicts periodic variations of luminosity when matter is supplied to the system at a constant accretion rate. These are related to the periodic appearance and disappearance of the Eddington Capture Sphere. In the model the frequency is found to vary inversely with the luminosity. If the input accretion rate varies (strictly) periodically, the luminosity variation is quasi-periodic, and the quality factor is inversely proportional to the relative amplitude of mass accretion fluctuations, with its largest value approximately Q= 1/(10 |delta Mdot/Mdot|) attained in oscillations at about 1 to 2 kHz frequencies for a 2 solar mass star

Synchrotron radiation from a runaway electron distribution in tokamaks

The synchrotron radiation emitted by runaway electrons in a fusion plasma provides information regarding the particle momenta and pitch-angles of the runaway electron population through the strong dependence of the synchrotron spectrum on these parameters. Information about the runaway density and its spatial distribution, as well as the time evolution of the above quantities, can also be deduced. In this paper we present the synchrotron radiation spectra for typical avalanching runaway electron distributions. Spectra obtained for a distribution of electrons are compared to the emission of mono-energetic electrons with a prescribed pitch-angle. We also examine the effects of magnetic field curvature and analyse the sensitivity of the resulting spectrum to perturbations to the runaway distribution. The implications for the deduced runaway electron parameters are discussed. We compare our calculations to experimental data from DIII-D and estimate the maximum observed runaway energy.Comment: 22 pages, 12 figures; updated author affiliations, fixed typos, added a sentence at the end of section I

Can Generic Products Be Disparaged? The Of and Concerning Requirement after Alar and the New Crop of Agricultural Disparagement Statutes

Under the group libel principle, a statement broadly critical of a large group generally cannot give rise to a defamation claim; it is said that such a statement does not refer to, or is not of and concerning, any particular individual. This Comment addresses the extent to which the of and concerning requirement and group libel principle apply to claims of product disparagement, a tort similar to defamation but encompassing pecuniary injury, as opposed to damage to reputation, resulting from false statements. In particular, this Comment examines whether speech generally critical of a generic product can give rise to disparagement liability. Recent statutes provide for such generic disparagement claims by agricultural producers, and one court, in the litigation resulting from the Alar controversy, has held the group libel rule does not bar such claims. This Comment concludes that, in most circumstances, the of and concerning requirement cannot be satisfied without a specific reference to the allegedly disparaged product and that generic disparagement claims usually should be barred, for both policy and constitutional reasons

Exploring the Relationship Between Adventist Hospital Board Chair Leadership Behaviors and Effectiveness

Problem and Purpose. There is a lack of empirical research regarding the leadership behaviors that predict an effective community hospital board chair. Researchers indicate that an effective organization normally has a well-led board. However, the chair role has been largely neglected in the research of board functions and operations. With many hospitals facing reorganization or closing, it is important to understand and identify effective chair behaviors. Thus, the purpose of this study was to determine the relationship between hospital chair leadership behaviors and effectiveness, and the relationship of effective chairs to effective hospitals. Method. This study used an ex post facto research design with stated and alternative hypotheses. The study was based upon a repeated measures design where the board chairs’ effectiveness and behaviors were measured more than once. An online survey using the Multifactor Leadership Questionnaire (MLQ) was administered to 333 board members serving 34 Adventist Health System hospitals. This survey measured board member perceptions of chair leadership behaviors and chair effectiveness. Patient satisfaction and clinical and financial data were also collected from each hospital to measure hospital effectiveness. Descriptive statistics, correlation, and multiple regression models were used to describe and examine the statistical relationship between variables. Of the 55 hypotheses tested, 34 (62%) were statistically significant and three others approached statistical significance. Results and Conclusions. The chairs reviewed by respondents were all Caucasian and male, ranging from 38 to 68 years old with 70% being 51 to 66 years of age. They had college education, ranging from bachelor’s degrees to doctorates, with 67% having master’s degrees. The chair’s length of service at their current facility ranged from 7 months to 12.9 years, with 55% serving 5 to 6 years. With the p value set at .05, correlations and multiple regression analysis revealed the following: 1. There was statistical significance and a positive relationship between transformational leadership behaviors and chair effectiveness (r = .869; p =.000). 2. There was statistical significance and a positive relationship between transactional leadership behaviors and chair effectiveness (r =.382; p =.000). 3. There was no statistically significant relationship between laissez-faire leadership behaviors and chair effectiveness (r = -.122; p = .178). 4. There was statistical significance and a positive relationship between financial margin; Earnings Before Interest, Taxes, Depreciation, and Amortization (EBITDA) and Clinical Outcomes (CM) (r = .331; p = .000). There was no statistical significance in the relationship between hospital financial margins and patient satisfaction (r = .169; p = .066). 5. There was no statistical significance in the relationship found between chair leadership effectiveness and hospital effectiveness metrics such as EBITDA (r = -.019; p = .831), Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS; r = -160; p = .083), and CM (r = -.044; p = .632). 6. There was statistical significance and a positive relationship between chair education and chair effectiveness (r =.235; p = .009). 7. There was statistical significance and a positive relationship between chair education and the organizational metric EBITDA (r = .349; p = .000) but no statistically significant relationship between chair education and patient satisfaction (r = -.043; p = .643). 8. There was no statistically significant relationship between chair longevity and chair effectiveness (r = -.023; p = .803). 9. There was a statistically significant relationship between chair longevity and patient satisfaction as measured by Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS; r =.221; p = .016). However, there was statistical significance and a negative relationship between chair longevity and hospital financial success as measured by EBITDA (r = -.233; p = .010). 10. While nearing statistical significance, there was no statistically significant relationship between chair age and chair effectiveness (r = -.169; p = .061). 11. There was statistical significance and a negative relationship between chair age and hospital financial performance as measured by EBITDA (r = -203, p = .024). Conclusions and Recommendations. In this study, both transformational and transactional leadership behaviors predicted chair effectiveness. The relationship between Laissez-faire leadership behaviors and effectiveness was not statistically significant (r = -.122; p = .178). In addition, the study showed chair education had a statistically significant relationship on the hospitals’ financial margins (r = .349; p = .000). Finally, while strong financial margins predicted clinical outcomes (r = .331; p = .000), they did not have a statistically significant relationship to patient satisfaction (r = .169; p = .066). Several recommendations to boards, hospitals, and researchers can be made from this study. First, given the significance of transformational and transactional leadership behaviors on chair effectiveness, boards may wish to screen potential chairs for these behaviors or provide training that facilitates the development of these behaviors. Second, given the significance of chair education on chair effectiveness and hospital financial margins, boards may wish to screen chairs for higher levels of education to better predict chair and hospital effectiveness. Finally, given this study was done only on Adventist Health System hospitals and only White male chairs, other researchers may wish to replicate this study in other healthcare systems with more diverse chairs. In addition, initiating a qualitative study of chairs would provide additional answers to questions raised in this study

Dust Formation and He II 4686 emission in the Dense Shell of the Peculiar Type Ib Supernova 2006jc

We present evidence for the formation of dust grains in an unusual Type Ib SN based on late-time spectra of SN 2006jc. The progenitor suffered an LBV-like outburst just 2 yr earlier, and we propose that the dust formation is a consequence of the SN blast wave overtaking that LBV-like shell. The key evidence for dust formation is (a) the appearance of a red/near-IR continuum source fit by 1600 K graphite grains, and (b) fading of the redshifted sides of He I emission lines, yielding progressively more asymmetric blueshifted lines as dust obscures receding material. This provides the strongest case yet for dust formation in any SN Ib/c. Both developments occurred between 51 and 75 d after peak, while other SNe observed to form dust did so after a few hundred days. Geometric considerations indicate that dust formed in the dense swept-up shell between the forward and reverse shocks, and not in the freely expanding SN ejecta. Rapid cooling leading to dust formation may have been aided by extremely high shell densities, as indicated by He I line ratios. The brief epoch of dust formation is accompanied by He II 4686 emission and enhanced X-ray emission. These clues suggest that the unusual dust formation in this object was not due to properties of the SN itself, but instead -- like most peculiarities of SN 2006jc -- was a consequence of the dense environment created by an LBV-like eruption 2 yr before the SN.Comment: ApJ, accepted. added some discussion and 2 figures, better title, conclusions same as previous version. 12 pages, 4 color fig