New lower bounds for the independence number of sparse graphs and hypergraphs

We obtain new lower bounds for the independence number of $K_r$-free graphs and linear $k$-uniform hypergraphs in terms of the degree sequence. This answers some old questions raised by Caro and Tuza \cite{CT91}. Our proof technique is an extension of a method of Caro and Wei \cite{CA79, WE79}, and we also give a new short proof of the main result of \cite{CT91} using this approach. As byproducts, we also obtain some non-trivial identities involving binomial coefficients

Source Regions of Coronal Mass Ejections

Observations of the solar corona with the Large Angle Spectrometric Coronograph (LASCO) and Extreme ultraviolet Imaging Telescope (EIT) instruments on the Solar and Heliospheric Observatory (SOHO) provide an unprecedented opportunity to study coronal mass ejections (CMEs) from their initiation through their evolution out to 30 \rsun. The objective of this study is to gain an understanding of the source regions from which the CMEs emanate. To this end, we have developed a list of 32 CMEs whose source regions are located on the solar disk and are well observed in EIT 195 {\AA} data during the period from so lar minimum in January 1996 through the rising part of the cycle in May 1998. We compare the EIT source regions with photospheric magnetograms from the Michelson Doppler Imager (MDI) instrument on SOHO and the NSO/Kitt Peak Observatory and also with H$\alpha$ data from various sources. The overall results of our study show that 41% of the CME related transients observed are associated with active regions and have no prominence eruptions, 44% are associated with eruptions of prominences embedded in active regions and 15% are associated with eruptions of prominences outside active regions. Those CMEs that do not involve prominence eruptions originate in active regions both with and without prominences. We describe 6 especially well observed events. These case studies suggest that active region CMEs (without eruptive prominences) are associated with active regions with lifetimes between 11--80 days. They are also often associated with small scale emerging or cancelling flux over timescales of 6--7 hours. CMEs associated with active region prominence eruptions, on the other hand, are typically associated with old active regions with lifetimes $\sim$ 6-7 months.Comment: Accepted for publication in ApJ, scheduled for Nov 1, 2001 issu

The Powerful Antitakeover Force of Staggered Boards: Theory, Evidence and Policy

Staggered boards, which a majority of public companies now have, provide a powerful antitakeover defense, stronger than is commonly recognized. They provide antitakeover protection both by (i) forcing any hostile bidder, no matter when it emerges, to wait at least one year to gain control of the board and (ii) requiring such a bidder to win two elections far apart in time rather than a one-time referendum on its offer. Using a new data set of hostile bids in the five-year period 1996-2000, we find that not a single hostile bid won a ballot box victory against an 'effective' staggered board (ESB). We also find that an ESB nearly doubled the odds of remaining independent for an average target in our data set, from 34% to 61%, halved the odds that a first bidder would be successful, from 34% to 14%, and reduced the odds of a sale to a white knight, from 32% to 25%. Furthermore, we find that the shareholders of targets that remained independent were made worse off compared with accepting the bid and that ESBs did not provide sufficient countervailing benefits in terms of increased premiums to offset the costs of remaining independent. Overall, we estimate that, in the period studied, ESBs reduced the returns of shareholders of hostile bid targets on the order of 8-10%. Finally, we show that most staggered boards were adopted before the developments in takeover doctrine that made ESBs such a potent defense.

Effect of oxygen concentration on the structural and magnetic properties of LaRh1/2Mn1/2O3 thin films

Epitaxial LaRh1/2Mn1/2O3 thin films have been grown on (001)-oriented LaAlO3 and SrTiO3 substrates using pulsed laser deposition. The optimized thin film samples are semiconducting and ferromagnetic with a Curie temperature close to 100 K, a coercive field of 1200 Oe, and a saturation magnetization of 1.7muB per formula unit. The surface texture, structural, electrical, and magnetic properties of the LaRh1/2Mn1/2O3 films was examined as a function of the oxygen concentration during deposition. While an elevated oxygen concentration yields thin films with optimal magnetic properties, slightly lower oxygen concentrations result in films with improved texture and crystallinity

Investigating the generalizability of EEG-based Cognitive Load Estimation Across Visualizations

We examine if EEG-based cognitive load (CL) estimation is generalizable across the character, spatial pattern, bar graph and pie chart-based visualizations for the nback~task. CL is estimated via two recent approaches: (a) Deep convolutional neural network, and (b) Proximal support vector machines. Experiments reveal that CL estimation suffers across visualizations motivating the need for effective machine learning techniques to benchmark visual interface usability for a given analytic task

Price Elasticity of Demand for Term Life Insurance and Adverse Selection

This paper provides an empirical estimate of price' and risk' elasticities of demand for term life insurance for those who purchase some insurance. It finds that the elasticity with respect to changes in premiums is generally higher than the elasticity with respect to changes in risk. It also finds that the elasticity, in the range of -0.3 to -0.5, is sufficiently low that adverse selection in term life insurance is unlikely to lead to a death spiral and may not even lead to measured effects of adverse selection on total purchases.