Regions of the T cell receptor alpha and beta chains that are responsible for interactions with CD3.

The T cell antigen receptor consists of the Ti alpha/beta heterodimer which recognizes antigen, and the associated CD3 chains, thought to be involved in signal transduction. To understand the nature of the interaction between Ti and CD3, chimeric molecules which included the COOH-terminal segments of Ti alpha or beta linked to the extracellular segment of CD8, were transfected into a mutant T cell deficient in Ti beta chain expression and cell surface CD3. Both chimeric chains were required to express the chimeric Ti and to restore CD3 surface expression. CD8/Ti and CD3 cointernalized and coimmunoprecipitated. Stimulation of the chimeric receptor induced transmembrane signaling events and cell activation. These results demonstrate that the Ti alpha and beta COOH termini containing the transmembrane domains are sufficient for structural and functional coupling of Ti to CD3

On integrability of a (2+1)-dimensional perturbed Kdv equation

A (2+1)-dimensional perturbed KdV equation, recently introduced by W.X. Ma and B. Fuchssteiner, is proven to pass the Painlev\'e test for integrability well, and its 4$\times$4 Lax pair with two spectral parameters is found. The results show that the Painlev\'e classification of coupled KdV equations by A. Karasu should be revised

Polarized antiquark flavor asymmetry: Pauli blocking vs. the pion cloud

The flavor asymmetry of the unpolarized antiquark distributions in the proton, dbar(x) - ubar(x) > 0, can qualitatively be explained either by Pauli blocking by the valence quarks, or as an effect of the pion cloud of the nucleon. In contrast, predictions for the polarized asymmetry Delta_ubar(x) - Delta_dbar(x) based on rho meson contributions disagree even in sign with the Pauli blocking picture. We show that in the meson cloud picture a large positive Delta_ubar(x) - Delta_dbar(x) is obtained from pi-N - sigma-N interference-type contributions, as suggested by chiral symmetry. This effect restores the equivalence of the 'quark' and 'meson' descriptions also in the polarized case.Comment: 4 pages, revtex, 3 eps figure

Coulomb Gas on the Keldysh Contour: Anderson-Yuval-Hamann representation of the Nonequilibrium Two Level System

The nonequilibrium tunnelling center model of a localized electronic level coupled to a fluctuating two-state system and to two electronic reservoirs, is solved via an Anderson-Yuval-Hamann mapping onto a plasma of alternating positive and negative charges time-ordered along the two "Keldysh" contours needed to describe nonequilibrium physics. The interaction between charges depends both on whether their time separation is small or large compared to a dephasing scale defined in terms of the chemical potential difference between the electronic reservoirs and on whether their time separation is larger or smaller than a decoherence scale defined in terms of the current flowing from one reservoir to another. A renormalization group transformation appropriate to the nonequilibrium problem is defined. An important feature is the presence in the model of a new coupling, essentially the decoherence rate, which acquires an additive renormalization similar to that of the energy in equilibrium problems. The method is used to study interplay between the dephasing-induced formation of independent resonances tied to the two chemical potentials and the decoherence which cuts off the scaling and leads to effectively classical long-time behavior. We determine the effect of departures from equilibrium on the localization-delocalization phase transition.Comment: discussion and references added, to appear in PR

Analyzing Firm Performance in the Insurance Industry Using Frontier Efficiency Methods

In this introductory chapter to an upcoming book, the authors discuss the two principal types of efficiency frontier methodologies - the econometric (parametric) approach and the mathematical programming (non-parametric) approach. Frontier efficiency methodologies are discussed as useful in a variety of contexts: they can be used for testing economic hypotheses; providing guidance to regulators and policymakers; comparimg economic performance across countries; and informing management of the effects of procedures and strategies adapted by the firm. The econometric approach requires the specification of a production, cost, revenue, or profit function as well as assumptions about error terms. But this methodology is vulnerable to errors in the specification of the functional form or error term. The mathematical programming or linear programming approach avoids this type of error and measures any departure from the frontier as a relative inefficiency. Because each of these methods has advantages and disadvantages, it is recommended to estimate efficiency using more than one method. An important step in efficiency analysis is the definition of inputs and outputs and their prices. Insurer inputs can be classified into three principal groups: labor, business services and materials, and capital. Three principal approaches have been used to measure outputs in the financial services sector: the asset or intermediation approach, the user-cost approach, and the value-added approach. The asset approach treats firms as pure financial intermediaries and would be inappropriate for insurers because they provide other services. The user-cost method determines whether a financial product is an input or output based on its net contribution to the revenues of the firm. This method requires precise data on products, revenues and opportunity costs which are difficult to estimate in insurance. The value-added approach is judged the most appropriate method for studying insurance efficiency. it considers all asset and liability categories to have some output characteristics rather than distinguishing inputs from outputs. In order to measure efficiency in the insurance industry in which outputs are mostly intangible, measurable services must be defined. The three principal services provided by insurance companies are risk pooling and risk-bearing, "real" financial services relating to insured losses, and intermediation. The authors discuss how these services can be measured as outputs in value-added analysis. They then summarize existing efficiency literature.

The structure, conduct, and regulation of the property-liability insurance industry

Insurance industry

Further explorations of Skyrme-Hartree-Fock-Bogoliubov mass formulas. XI: Stabilizing neutron stars against a ferromagnetic collapse

We construct a new Hartree-Fock-Bogoliubov (HFB) mass model, labeled HFB-18, with a generalized Skyrme force. The additional terms that we have introduced into the force are density-dependent generalizations of the usual $t_1$ and $t_2$ terms, and are chosen in such a way as to avoid the high-density ferromagnetic instability of neutron stars that is a general feature of conventional Skyrme forces, and in particular of the Skyrme forces underlying all the HFB mass models that we have developed in the past. The remaining parameters of the model are then fitted to essentially all the available mass data, an rms deviation $\sigma$ of 0.585 MeV being obtained. The new model thus gives almost as good a mass fit as our best-fit model HFB-17 ($\sigma$ = 0.581 MeV), and has the advantage of avoiding the ferromagnetic collapse of neutron stars.Comment: accepted for publication in Physical Review

Monitoring the Impact of Health Reform on Americans 50-64: Medicaid Expansion and Marketplace Implementation Increased Health Coverage

This survey shows that the share of 50- to 64-year-olds without health insurance fell between December 2013 and March 2014. In states that expanded their Medicaid programs, a greater share of previously uninsured adults gained coverage, particularly among groups that have traditionally faced barriers to obtaining it. The survey also found that the newly insured differed in key ways from those who reported being insured for all of the past 12 months. On average, more were low income, and more reported that they had had trouble paying medical bills. This paper is part of a series that looks at the experience of 50- to 64-year-olds during the first open enrollment period of the Affordable Care Act (ACA)