Direct measurement of energetic electrons coupling to an imploding low-adiabat inertial confinement fusion capsule

We have imaged hard x-ray (>100 keV) bremsstrahlung emission from energetic electrons slowing in a plastic ablator shell during indirectly driven implosions at the National Ignition Facility. We measure 570 J in electrons with E>100 keV impinging on the fusion capsule under ignition drive conditions. This translates into an acceptable increase in the adiabat α, defined as the ratio of total deuterium-tritium fuel pressure to Fermi pressure, of 3.5%. The hard x-ray observables are consistent with detailed radiative-hydrodynamics simulations, including the sourcing and transport of these high energy electrons.     

The measurement of pressure-induced shifts and widths of the (J, K) = (3, 3) inversion line of NH3 at various temperatures

Line-shift and line-width parameters for the (J, K) = (3, 3) inversion line of N¹⁴H₃ have been measured at various temperatures in the range 213 to 373 K, and the results are compared with those predicted theoretically. The line-width parameter decreases with increasing temperature, in qualitative agreement with the theory, but the predicted widths are between 10 and 20% too large. The line-shift parameter is positive, so that the center frequency of the spectral line increases with increasing pressure, and the parameter decreases with increasing temperature. This is also in qualitative agreement with the theory but the predicted results are too large by factors of between 3.8 and 7.2. In addition to the experimental results, details are also given of a number of improvements which have been made to the spectrometer which had been used for earlier shift measurements.     

Mechanism of solid|liquid interfacial reactions. The reactive dissolution of p-chloranil in aqueous solution as studied by the channel flow cell with electrochemical detection and atomic force microscopy

A quantitative study of the hydrolytic dissolution of solid p-chloranil at alkaline pH using a combination of the channel flow cell and in situ atomic force microscopy measurements shows that the dissolution is driven by reaction of the substrate with hydroxide ions at, or very close to, the dissolving surface. The dissolution rate equation, deduced from the channel flow cell for single crystals of p-chloranil, is rate/mol cm⁻² s⁻¹ = 3.8 × 10⁻⁷ [OH⁻]₀ where [OH⁻]₀/M is the hydroxide ion concentration adjacent to the solid surface. An analogous rate law is derived for pressed pellet substrates. The novel application of the atomic force microscope to make absolute measurements of surface averaged dissolution rates is described. Comparison with the independent channel flow cell data reveals good mechanistic agreement and consistency of rate constants provided it is recognised that a thick stagnant diffusion layer can be present under the usual conditions employed for AFM.     

DETECTION OF PORPHYRIN EXCITED STATES IN THE INTACT BOVINE LENS

Previous steady state and time resolved spectroscopic studies on porphyrins have shown that the triplet lifetimes of those sensitizers that bind to lens proteins are lengthened by several orders of magnitude. Presented here is an extension of this experiment to measure these transients in an intact bovine lens. As demonstrated by steady state fluorescence spectroscopy and flash photolysis, mesotetra (p-sulfonatophenyl)porphyrin (TPPS) binds to lens proteins. In air-saturated aqueous solution, TPPS has a triplet lifetime of 2 microseconds. In an intact bovine lens the triplet state decayed via biexponential kinetics with lifetimes of 0.16 and 1.6 microseconds. In addition to a lengthening of the lifetime there was a red shift in the triplet transient spectra of 10-20 nm of the porphyrin in the intact lenses.     

Efficient Hydrolysis of RNA by a PNA - Diethylenetriamine Adduct

The introduction of a urea bond linking a protected diethylenetriamine (DETA) unit and the terminal amino group of a resin-bound peptide nucleic acid (PNA) decamer gave access to a PNA - DETA adduct (shown here), which hydrolyzed the target 25-mer RNA rapidly and sequence specifically.     

Stability of fluorenylemthoxycarbonylamino groups in peptide synthesis. Cleavage by hydrogenolysis and by dipolar aprotic solvents

$\text{N}$-Fluorenylmethoxycarbonyl derivatives of amines are unexpectedly cleaved by catalytic hydrogenation with t$\text{1}\text{2}$ 3–33 h. under various conditions. They are also cleaved on standing in the solvents dimethylformamide, dimethylacetamine, and $\text{N}$-methylpyrrolidone, but much more slowly.     

THE EFFECT OF MERCURIC IONS ON THE EXCITED STATES OF DNA-INTERCALATED ETHIDIUM BROMIDE

The first excited triplet state of DNA-intercalated ethidium bromide is produced with a quantum yield of 0.010.002 on irradiation at 532 nm. A difference extinction coefficient of 1.50.210³ m² mol^?1 is measured for the triplet state at 380 nm. Mercuric ions quench the first excited singlet state of DNA-intercalated ethidium bromide via induced spin orbit coupling to give an increased yield of ethidium triplet states. The same mercuric ion that quenches the singlet state then quenches the triplet state, via the same mechanism, with a rate constant of ca 3.510³ s^?1. An upper limit for the rate of detachment of Hg²⁺ from its binding site in DNA may be fixed at ca 10³ s^?1.