9,856 research outputs found
Four dimensional "old minimal" N=2 supersymmetrization of R^4
We write in superspace the lagrangian containing the fourth power of the Weyl
tensor in the "old minimal" d=4, N=2 supergravity, without local SO(2)
symmetry. Using gauge completion, we analyze the lagrangian in components. We
find out that the auxiliary fields which belong to the Weyl and compensating
vector multiplets have derivative terms and therefore cannot be eliminated
on-shell. Only the auxiliary fields which belong to the compensating nonlinear
multiplet do not get derivatives and could still be eliminated; we check that
this is possible in the leading terms of the lagrangian. We compare this result
to the similar one of "old minimal" N=1 supergravity and we comment on possible
generalizations to other versions of N=1,2 supergravity.Comment: 31 pages, no figures. Minor corrections. Details of the full
calculation included as an appendix. Reference adde
A new photon recoil experiment: towards a determination of the fine structure constant
We report on progress towards a measurement of the fine structure constant to
an accuracy of or better by measuring the ratio of the
Planck constant to the mass of the cesium atom. Compared to similar
experiments, ours is improved in three significant ways: (i) simultaneous
conjugate interferometers, (ii) multi-photon Bragg diffraction between same
internal states, and (iii) an about 1000 fold reduction of laser phase noise to
-138 dBc/Hz. Combining that with a new method to simultaneously stabilize the
phases of four frequencies, we achieve 0.2 mrad effective phase noise at the
location of the atoms. In addition, we use active stabilization to suppress
systematic effects due to beam misalignment.Comment: 12 pages, 9 figure
Lack of uniqueness for weak solutions of the incompressible porous media equation
In this work we consider weak solutions of the incompressible 2-D porous
media equation. By using the approach of De Lellis-Sz\'ekelyhidi we prove
non-uniqueness for solutions in in space and time.Comment: 23 pages, 2 fugure
Decoding sequence-level information to predict membrane protein expression
The expression and purification of integral membrane proteins remains a major bottleneck in the characterization of these important proteins. Expression levels are currently unpredictable, which renders the pursuit of these targets challenging and highly inefficient. Evidence demonstrates that small changes in the nucleotide or amino-acid sequence can dramatically affect membrane protein biogenesis; yet these observations have not resulted in generalizable approaches to improve expression. In this study, we develop a data-driven statistical model that predicts membrane protein expression in E. coli directly from sequence. The model, trained on experimental data, combines a set of sequence-derived variables resulting in a score that predicts the likelihood of expression. We test the model against various independent datasets from the literature that contain a variety of scales and experimental outcomes demonstrating that the model significantly enriches expressed proteins. The model is then used to score expression for membrane proteomes and protein families highlighting areas where the model excels. Surprisingly, analysis of the underlying features reveals an importance in nucleotide sequence-derived parameters for expression. This computational model, as illustrated here, can immediately be used to identify favorable targets for characterization
NO CALOR DA OBRA: ENCONTROS COM A PRODUÇÃO CULTURAL CONTEMPORÂNEA Entrevista com o escritor Moacyr Scliar
NO CALOR DA OBRA: ENCONTROS COM A PRODUÇÃOCULTURAL CONTEMPORÂNEA Entrevista com o escritor Moacyr Sclia
Near--K-edge double and triple detachment of the F- negative ion: observation of direct two-electron ejection by a single photon
Double and triple detachment of the F-(1s2 2s2 2p6) negative ion by a single
photon have been investigated in the photon energy range 660 to 1000 eV. The
experimental data provide unambiguous evidence for the dominant role of direct
photo-double-detachment with a subsequent single-Auger process in the reaction
channel leading to F2+ product ions. Absolute cross sections were determined
for the direct removal of a (1s+2p) pair of electrons from F- by the absorption
of a single photon
- …