387 research outputs found
Elongation dynamics of amyloid fibrils: a rugged energy landscape picture
Protein amyloid fibrils are a form of linear protein aggregates that are
implicated in many neurodegenerative diseases. Here, we study the dynamics of
amyloid fibril elongation by performing Langevin dynamic simulations on a
coarse-grained model of peptides. Our simulation results suggest that the
elongation process is dominated by a series of local minimum due to frustration
in monomer-fibril interactions. This rugged energy landscape picture indicates
that the amount of recycling of monomers at the fibrils' ends before being
fibrilized is substantially reduced in comparison to the conventional two-step
elongation model. This picture, along with other predictions discussed, can be
tested with current experimental techniques
Expanding Economic Opportunity for More Americans: Bipartisan Policies to Increase Work, Wages, and Skills
Many workers today find themselves lacking the skills and training necessary to thrive in the modern economy. Most low- and middle-income workers have not seen meaningful wage increases in many years. Millions of men and women are missing from the workforce altogether. These challenges stem from profound shifts in the American economy and necessitate a dedicated policy response.Over the course of the past year, the Aspen Economic Strategy Group collected policy ideas to address the barriers to broad-based economic opportunity and identified concrete proposals with bipartisan appeal. These proposals are presented here
Search for First Generation Scalar Leptoquark Pairs in ppbar Collisions at sqrt(s)=1.8 TeV
We have searched for first generation scalar leptoquark (LQ) pairs in the
enu+jets channel using ppbar collider data (integrated luminosity= 115 pb^-1)
collected by the DZero experiment at the Fermilab Tevatron during 1992-96. The
analysis yields no candidate events. We combine the results with those from the
ee+jets and nunu+jets channels to obtain 95% confidence level (CL) upper limits
on the LQ pair production cross section as a function of mass and of beta, the
branching fraction to a charged lepton. Comparing with the next-to-leading
order theory, we set 95% CL lower limits on the LQ mass of 225, 204, and 79
GeV/c^2 for beta=1, 1/2, and 0, respectively.Comment: 14 pages, 4 figures, submitted to Physical Review Letters Replaced to
correct visitor addresse
Direct Measurement of the Top Quark Mass at D0
We determine the top quark mass m_t using t-tbar pairs produced in the D0
detector by \sqrt{s} = 1.8 TeV p-pbar collisions in a 125 pb^-1 exposure at the
Fermilab Tevatron. We make a two constraint fit to m_t in t-tbar -> b W^+bbar
W^- final states with one W boson decaying to q-qbar and the other to e-nu or
mu-nu. Likelihood fits to the data yield m_t(l+jets) = 173.3 +- 5.6 (stat) +-
5.5 (syst) GeV/c^2. When this result is combined with an analysis of events in
which both W bosons decay into leptons, we obtain m_t = 172.1 +- 5.2 (stat) +-
4.9 (syst) GeV/c^2. An alternate analysis, using three constraint fits to fixed
top quark masses, gives m_t(l+jets) = 176.0 +- 7.9 (stat) +- 4.8 (syst)
GeV/C^2, consistent with the above result. Studies of kinematic distributions
of the top quark candidates are also presented.Comment: 43 pages, 53 figures, 33 tables. RevTeX. Submitted to Phys. Rev.
Limits on Anomalous WWgamma and WWZ Couplings
Limits on the anomalous WWgamma and WWZ couplings are presented from a
simultaneous fit to the data samples of three gauge boson pair final states in
pbar-p collisions at sqrt(s)=1.8 TeV: Wgamma production with the W boson
decaying to enu or munu, W boson pair production with both of the W bosons
decaying to enu or munu, and WW or WZ production with one W boson decaying to
enu and the other W boson or the Z boson decaying to two jets. Assuming
identical WWgamma and WWZ couplings, 95 % C.L. limits on the anomalous
couplings of -0.30<Delta kappa<0.43 (lambda = 0) and -0.20<lambda<0.20 (Delta
kappa = 0) are obtained using a form factor scale Lambda = 2.0 TeV. Limits
found under other assumptions on the relationship between the WWgamma and WWZ
couplings are also presented.Comment: 13 pages, 3 figures, submitted to Physical Review
Measurement of the Boson Mass
A measurement of the mass of the boson is presented based on a sample of
5982 decays observed in collisions at
= 1.8~TeV with the D\O\ detector during the 1992--1993 run. From a
fit to the transverse mass spectrum, combined with measurements of the
boson mass, the boson mass is measured to be .Comment: 12 pages, LaTex, style Revtex, including 3 postscript figures
(submitted to PRL
- …