Measurement of the 6Li(e,e'p) reaction cross sections at low momentum transfer

The triple differential cross sections for the 6Li(e,e'p) reaction have been measured in the excitation energy region from 27 to 46 MeV in a search for evidence of the giant dipole resonance (GDR) in 6Li. The cross sections have no distinct structures in this energy region, and decrease smoothly with the energy transfer. Angular distributions are different from those expected with the GDR. Protons are emitted strongly in the momentum-transfer direction. The data are well reproduced by a DWIA calculation assuming a direct proton knockout process.Comment: 19 pages, 7 figures, revised text, to be published in Nucl. Phys.

Structural basis for the inhibition of RecBCD by Gam and its synergistic antibacterial effect with quinolones

Our previous paper (Wilkinson et al, 2016) used high-resolution cryo-electron microscopy to solve the structure of the Escherichia coli RecBCD complex, which acts in both the repair of double-stranded DNA breaks and the degradation of bacteriophage DNA. To counteract the latter activity, bacteriophage λ encodes a small protein inhibitor called Gam that binds to RecBCD and inactivates the complex. Here, we show that Gam inhibits RecBCD by competing at the DNA-binding site. The interaction surface is extensive and involves molecular mimicry of the DNA substrate. We also show that expression of Gam in E. coli or Klebsiella pneumoniae increases sensitivity to fluoroquinolones; antibacterials that kill cells by inhibiting topoisomerases and inducing double-stranded DNA breaks. Furthermore, fluoroquinolone-resistance in K. pneumoniae clinical isolates is reversed by expression of Gam. Together, our data explain the synthetic lethality observed between topoisomerase-induced DNA breaks and the RecBCD gene products, suggesting a new co-antibacterial strategy

Experiments at MIT-Bates(I. Nuclear Physics)

We have been collaborating with a group of University of Massachusetts since 1988 for experiments at MIT-Bates. Bates Experiment #89-09 (Measurement of the Elastic Magnetic Form Factor and the Threshold Breakup of ^3He at High Momentum Transfer) was accepted in 1989 and performed in 1997. Data analysis of the experiment was completed using one and a half years. A new proposal, Bates-Experiment #97-03 (Virtual Compton Scattering on the Proton Below Pion Threshold) has been scheduled in the early summer of 2000

Measurements of the Generalized Electric and Magnetic Polarizabilities of the Proton at Low Q2 Using the VCS Reaction

The mean square polarizability radii of the proton have been measured for the first time in a virtual Compton scattering experiment performed at the MIT-Bates out-of-plane scattering facility. Response functions and polarizabilities obtained from a dispersion analysis of the data at Q2=0.06 GeV2/c2 are in agreement with O(p3) heavy baryon chiral perturbation theory. The data support the dominance of mesonic effects in the polarizabilities, and the increase of beta with increasing Q2 is evidence for the cancellation of long-range diamagnetism by short-range paramagnetism from the pion cloud

Investigation of the conjectured nucleon deformation at low momentum transfer

We report new precise H$(e,e^\prime p)\pi^0$ measurements at the $\Delta(1232)$ resonance at $Q^2= 0.127$ (GeV/c)$^2$ using the MIT/Bates out-of-plane scattering (OOPS) facility. The data reported here are particularly sensitive to the transverse electric amplitude ($E2$) of the $\gamma^* N\to\Delta$ transition. Analyzed together with previous data yield precise quadrupole to dipole amplitude ratios $EMR = (-2.3 \pm 0.3_{stat+sys} \pm 0.6_{model})$ and $CMR = (-6.1 \pm 0.2_{stat+sys}\pm 0.5_{model})$ and for $M^{3/2}_{1+} = (41.4 \pm 0.3_{stat+sys}\pm 0.4_{model})(10^{-3}/m_{\pi^+})$. They give credence to the conjecture of deformation in hadronic systems favoring, at low $Q^2$, the dominance of mesonic effects.Comment: 4 pages, 1figur

Measurement of the Partial Cross Sections s(TT), s(LT) and [s(T)+epsilon*s(L)] of the p(e,e' pi+)n Reaction in the Delta(1232) Resonance

We report new precision p(e,e' pi+})n measurements in the Delta(1232) resonance at Q2 = 0.127(GeV/c)2 obtained at the MIT-Bates Out-Of-Plane scattering facility. These are the lowest, but non-zero, Q2 measurements in the pi+ channel. The data offer new tests of the theoretical calculations, particularly of the background amplitude contributions. The chiral effective field theory and Sato-Lee model calculations are not in agreement with this experiment