Nonlinear dynamics of a dense two-dimensional dipolar exciton gas

We use a simple model to describe the nonlinear dynamics of a dense two dimensional dipolar exciton gas. The model predicts an initial fast expansion due to dipole-dipole pressure, followed by a much slower diffusion. The model is in very good agreement with recent experimental results. We show that the dipole pressure induced expansion strongly constrains the time available for achieving and observing Bose-Einstein quantum statistical effects, indicating a need for spatial exciton traps. We also suggest that nonlinear ballistic exciton transport due to the strong internal dipole pressure is readily achievable.Comment: 5 pages, 4 figure

INFANTS - MINORITY AS A DEFENSE TO RESCISSION FOR FRAUD

Two defendants, one of whom was a minor, sold a business to the plaintiff. The plaintiff, in seeking to rescind the contract on the ground that it was induced by fraud, obtained a decree declaring the contract cancelled, and judgment was entered against the defendants for the sums they had received from the plaintiff. The minor defendant filed a petition to vacate the judgment as to him because during the trial no guardian ad litem had been appointed to represent him. Held, defendant is entitled to a new trial only if he could have made a good defense, and here since the plea of infancy, which the defendant wished to make, would not have defeated the plaintiff\u27s action, the petition is denied. Beardsley v. Clark, (Iowa, 1940) 294 N. W. 887

INSURANCE - INSURABLE INTEREST - OCCUPANT OR POSSESSOR OF REALTY

Plaintiff sued upon an insurance policy, issued to her by the defendant, covering a building in which she was conducting a merchandising business. The building was owned in fee by the plaintiff\u27s father-in-law, who had told the plaintiff that she might occupy it so long as she wished, and that he intended to deed it to her and her children. Held, plaintiff had an insurable interest in the building. Liverpool & London & Globe Ins. Co. v. Bolling, (Va. 1940) 10 S. E. (2d) 518

PRINCIPAL AND SURETY - EFFECT OF RELEASE OF PRINCIPAL DEBTOR WITH RESERVATION OF RIGHTS AGAINST SURETY

Plaintiff leased property to defendant, who in turn assigned his rights under the lease to one Garber, the latter assuming the covenants to pay rent and against commission of waste. Plaintiff did not release defendant from the lease. After the expiration of the lease plaintiff recovered judgment for $2,844.75 against defendant, for breaches of the covenants, and then recovered a similar judgment against Garber. Subsequently Garber paid the plaintiff$2,000, and plaintiff gave him a receipt acknowledging full satisfaction of the judgment rendered against me in the within action. The receipt of said sum is not a release of any legal right of the plaintiff herein to enforce his judgment against defendant in cause No. A 35993. Now plaintiff seeks to have his judgment declared a lien on property owned by the defendant. Held, the principal debtor by the terms of the release was fully discharged from the debt and therefore the reservation of right to enforce the claim against the surety was ineffectual. Gholson v. Savil, 137 Ohio St. 551, 31 N. E. (2d) 858 (1941)

Two-dimensional order in β-sheet peptide monolayers

Amphiphilic peptides comprising alternating hydrophilic and hydrophobic amino acid residues were designed to form super-secondary structures composed of self-assembled β-strands as monolayers at the air−water interface. Insights provided by in situ grazing-incidence X-ray diffraction (GIXD), surface pressure vs area isotherms, and Fourier transform infrared spectroscopy allow structural characterization of the assembled nanostructures and rational correlation with the peptide sequence. Peptides seven to seventeen amino acids in length were found to form crystalline arrays with coherence lengths in the range of 100 to 1000 Å. Two-dimensional registry of the self-assembled peptides was induced by placement of proline residues at the peptide termini. The films were found to intercalate ordered arrays of ions between juxtaposed β-sheet ribbons to generate peptide−ion composite phases

CHARITIES - TORTS - LIABILITY OF CHARITABLE CORPORATIONS FOR THEIR TORTS

Plaintiff was employed by defendant to assist in the work of redecorating defendant\u27s building, and was injured because of defendant\u27s alleged failure to provide a suitable place to work. To plaintiff\u27s plea for damages defendant answered that since it was a charitable corporation it was, therefore, immune from such action. Held, charitable corporations are not immune from liability for torts by reason of any exemption accorded them on the basis of the purposes for which they were incorporated. Gable v. Salvation Army, 186 Okla. 687, 100 P. (2d) 244 (1940)

APPEAL AND ERROR - BAD FAITH OF COUNSEL AS A BASIS FOR GRANTING A NEW TRIAL WHERE FACT THAT DEFENDANT WAS INSURED WAS BROUGHT TO ATTENTION OF JURY

It is generally agreed that the jury in a personal injury action should not be informed that the defendant is covered by indemnity insurance. The reasons for the rule are that the matter of insurance is irrelevant, and that the exposition of its existence is prejudicial. The jury is likely to grant more and larger verdicts for the plaintiff when it is known that an insurance company, rather than the individual defendant being tried, will have to pay the judgment. However, the fact that the defendant is insured reaches the jury in a multitude of ways. While direct evidence of insurance is inadmissible as such, it may be introduced if it bears on· some material issue. Also, the jury is quick to realize that an insurance company is involved when, upon the voir dire examination, each prospective juror is questioned as to his and his family\u27s interest in any insurance company. Often the matter comes in inadvertently, as where the witness\u27 answer mentioning insurance is unresponsive to the question asked. Finally it may be brought to the jury\u27s attention through the wilful misconduct of counsel. In those exceptional situations where evidence of insurance is admissible the introduction of such evidence clearly does not constitute error, but when the matter of insurance is clearly inadmissible, and yet the matter does get before the jury, many courts will grant the defendant a new trial if the opposing counsel acted wilfully, and will deny a new trial if opposing counsel acted in good faith. This comment is addressed to this distinction

Correlations in a two-dimensional Bose gas with long range interactions

We study the correlations of two-dimensional dipolar excitons in coupled quantum wells with a dipole -- dipole repulsive interaction. We show that at low concentrations, the Bose degeneracy of the excitons is accompanied by strong multi-particle correlations and the system behaves as a Bose liquid. At high concentration the particles interaction suppresses quantum coherence and the system behaves similar to a classical liquid down to a temperature lower than typical for a Bose gas. We evaluate the interaction energy per particle and the resulting blue shift of the exciton luminescence that is a direct tool to measure the correlations. This theory can apply to other systems of bosons with extended interaction.Comment: 11 pages including 2 figure

Microscale swimming: The molecular dynamics approach

The self-propelled motion of microscopic bodies immersed in a fluid medium is studied using molecular dynamics simulation. The advantage of the atomistic approach is that the detailed level of description allows complete freedom in specifying the swimmer design and its coupling with the surrounding fluid. A series of two-dimensional swimming bodies employing a variety of propulsion mechanisms -- motivated by biological and microrobotic designs -- is investigated, including the use of moving limbs, changing body shapes and fluid jets. The swimming efficiency and the nature of the induced, time-dependent flow fields are found to differ widely among body designs and propulsion mechanisms.Comment: 5 pages, 3 figures (minor changes to text

Velocity fluctuations and hydrodynamic diffusion in sedimentation

We study non-equilibrium velocity fluctuations in a model for the sedimentation of non-Brownian particles experiencing long-range hydrodynamic interactions. The complex behavior of these fluctuations, the outcome of the collective dynamics of the particles, exhibits many of the features observed in sedimentation experiments. In addition, our model predicts a final relaxation to an anisotropic (hydrodynamic) diffusive state that could be observed in experiments performed over longer time ranges.Comment: 7 pages, 5 EPS figures, EPL styl