Monitoring Dissociation Kinetics during Electrophoretic Focusing to Enable High‐Specificity Nucleic Acid Detection

A wide range of medical conditions can be diagnosed through sequence‐specific analysis of nucleic acids. However, a major challenge remains in detecting a specific target in samples containing a high concentration of mismatching sequences. A single‐step kinetic homogenous (free solution) assay is presented in which free sequence‐specific probes are continuously separated from probe–target hybrids during electrophoretic sample focusing, allowing monitoring of dissociation kinetics. Under these conditions, the different kinetics of targets versus mismatches result in distinct patterns of the signal (for example, linear increase for target versus exponential decay for mismatch), allowing the detection of desired sequences even in the presence of high background nucleic acid content. Additionally, an analytical model provides insight into the underlying dynamics, and allows design of assays based on this mechanism.     

Precision Rosenbluth measurement of the proton elastic form factors

We report the results of a new Rosenbluth measurement of the proton electromagnetic form factors at Q2 values of 2.64, 3.20, and 4.10 GeV2. Cross sections were determined by detecting the recoiling proton, in contrast to previous measurements which detected the scattered electron. Cross sections were determined to 3%, with relative uncertainties below 1%. The ratio mu(p)G(E)/G(M) was determined to 4%-8% and showed mu(p)G(E)/G(M) approximately 1. These results are consistent with, and much more precise than, previous Rosenbluth extractions. They are inconsistent with recent polarization transfer measurements of similar precision, implying a systematic difference between the techniques.     

Fission characteristics of the composite system 32S+50Ti: (I). Correlations between coincident fragments

The characteristics of “fission-like” processes observed in the bombardment of ⁵⁰Ti with ³²S ions of 140 MeV energy are investigated in a coincidence experiment between a time-of-flight telescope and a position sensitive ΔE-E ionization chamber. Coincident particles were identified and their energy and angular correlations in and normal to the reaction plane were measured. The experiment proves the binary nature of the mass division. Both the width and the average value of the total kinetic energy distribution are consistent with the values extrapolated from fission of heavier nuclei. An average number of 3±1 nucleons are emitted during the reaction; α-particle emission is not an important decay mode.