Coulomb excitation of the 242m Am isomer

The ^242m Am isomer, a well-known candidate for photodepopulation research, has been studied in this first ever Coulomb excitation of a nearly pure (≈98%) isomer target. Thirty new states, including a new rotational band built on a K ^π = 6^? state, have been identified. Strong K-mixing results in nearly equal populations of the K ^π=5^? and 6^? states. Newly identified states have been assigned to the K ^π=3^? rotational band, the lowest states of which are known to decay into the ground-state band. Implications regarding K-mixing and Coulomb excitation paths to the ground state are discussed.     

First staging of two laser accelerators

Staging of two laser-driven, relativistic electron accelerators has been demonstrated for the first time in a proof-of-principle experiment, whereby two distinct and serial laser accelerators acted on an electron beam in a coherently cumulative manner. Output from a CO2 laser was split into two beams to drive two inverse free electron lasers (IFEL) separated by 2.3 m. The first IFEL served to bunch the electrons into approximately 3 fs microbunches, which were rephased with the laser wave in the second IFEL. This represents a crucial step towards the development of practical laser-driven electron accelerators.     

Anion-exchange paper chromatography of metal ions

The migration of 26 ions on anion-exchange paper is studied with five different complexing solvents. The results are reported as a function of the sign of the charge on each ion determined electrochromatographically. Several possible separations are presented, but it is shown that the prediction of separations, knowing only the charge on several substances, is impossible. It is also demonstrated that ion-exchange column experiments and ion-exchange paper experiments do not necessarily yield identical results.     

Trennung der Xylole und Xthylbenzol durch extraktive Kristallisation mit Thioharnstoff

Ohne Zusammenfassung     

PBW deformations of quadratic monomial algebras

A result of Braverman and Gaitsgory from 1996 gives necessary and sufficient conditions for a filtered algebra to be a Poincaré-Birkhoff-Witt (PBW) deformation of a Koszul algebra. The main theorem in this paper establishes conditions equivalent to the Braverman-Gaitsgory Theorem to efficiently determine PBW deformations of quadratic monomial algebras. In particular, a graphical interpretation is presented for this result, and we discuss circumstances under which some of the conditions of this theorem need not be checked. Several examples are also provided. Finally, with these tools, we show that each quadratic monomial algebra admits a nontrivial PBW deformation.     

Optimal kernel estimation of densities

Precise asymptotic behavior for mean integrated squared error (MISE) is determined for sequences of kernel estimators of a density in a broad class, including discontinuous and possibly unbounded densities. The paper shows that the sequence using the kernel optimal at each fixed sample size is asymptotically more efficient than a sequence generated by changing the bandwidth of a fixed kernel shape, regardless of the kernel shape. The class of densities considered are those whose characteristic functions behave at large arguments like the product of a Fourier series and a regularly varying function. This condition may be related to the smoothness of an m-th derivative of the density.Partially supported by National Science Foundation Grant DMS-8711924.