Disentangling Forms of Lorentz Violation With Complementary Clock Comparison Experiments

Atomic clock comparisons provide some of the most precise tests of Lorentz and CPT symmetries in the laboratory. With data from multiple such experiments using different nuclei, it is possible to constrain new regions of the parameter space for Lorentz violation. Relativistic effects in the nuclei allow us to disentangle forms of Lorentz violation which could not be separately measured in purely nonrelativistic experiments. The disentangled bounds in the neutron sectors are at the 10^(-28) GeV level, far better than could be obtained with any other current technique.Comment: 9 page

Epitope mapping using mRNA display and a unidirectional nested deletion library

In vitro selection targeting an anti-polyhistidine monoclonal antibody was performed using mRNA display with a random, unconstrained 27-mer peptide library. After six rounds of selection, epitope-like peptides were identified that contain two to five consecutive, internal histidines and are biased for arginine residues, without any other identifiable consensus. The epitope was further refined by constructing a high-complexity, unidirectional fragment library from the final selection pool. Selection by mRNA display minimized the dominant peptide from the original selection to a 15-residue functional sequence (peptide Cmin: RHDAGDHHHHHGVRQ; K-D = 38 nM). Other peptides recovered from the fragment library selection revealed a separate consensus motif (ARRXA) C-terminal to the histidine track. Kinetics measurements made by surface plasmon resonance, using purified Fab (antigen-binding fragment) to prevent avidity effects, demonstrate that the selected peptides bind with 10- to 75-fold higher affinities than a hexahistidine peptide. The highest affinity peptides (K-D approximate to 10 nM) encode both a short histidine track and the ARRXA motif, suggesting that the motif and other flanking residues make important contacts adjacent to the core polyhistidine-binding site and can contribute > 2.5 kcal/mol of binding free energy. The fragment library construction methodology described here is applicable to the development of high-complexity protein or cDNA expression libraries for the identification of protein-protein interaction domains

Why health care matters and the current debt does not

All of the attention given to raising the debt ceiling this past summer might lead some to believe that spending by the federal government only recently became unsustainable. Hardly. We've been on this path a long time.Health care reform ; Debt

Capital controls by any other name

The embrace of ad hoc capital controls to address temporary market inefficiencies on a case-by-case basis, while pragmatic, perpetuates the view that each capital crisis is an isolated example of failed financial institutions.Capital market

Commodity price gains: speculation vs. fundamentals

Commodities of all sorts have risen in price over the past few years. Some say that the prices reflect a bubble, driven by low interest rates and excessive speculation. Others say the price gains can be fully explained by supply and demand.Inflation (Finance) ; Food prices

Why "fixing" China's currency is no quick fix

Even if China does revalue its currency, jobs aren’t likely to come flooding back to the United States. Much of what China exports to the U.S. originates in other Asian countries.Foreign exchange rates ; International finance ; China

Monetary policy and asset prices

The housing market crisis is the latest reminder that asset prices can and do run wild at rates capable of negative effects on real economic activity. Not surprisingly, this has reinvigorated debate over whether central banks should respond to asset price bubbles.Monetary policy ; Asset pricing