Three dimensional anisotropic κ spectra of turbulence at subproton scales in the solar wind.

We show the first three dimensional (3D) dispersion relations and k spectra of magnetic turbulence in the solar wind at subproton scales. We used the Cluster data with short separations and applied the k-filtering technique to the frequency range where the transition to subproton scales occurs. We show that the cascade is carried by highly oblique kinetic Alfvén waves with ω(plas) ≤ 0.1ω(ci) down to k(⊥) ρ(i)∼2. Each k spectrum in the direction perpendicular to B0 shows two scaling ranges separated by a breakpoint (in the interval [0.4,1]k(⊥)ρ(i): a Kolmogorov scaling k(⊥)⁻¹â±7 followed by a steeper scaling ∼k(⊥)⁻4ⁱ5. We conjecture that the turbulence undergoes a transition range, where part of the energy is dissipated into proton heating via Landau damping and the remaining energy cascades down to electron scales where electron Landau damping may predominate.

Anisotropic turbulent spectra in the terrestrial magnetosheath as seen by the cluster spacecraft.

Here we report the first three-dimensional spatial spectrum of the low frequency magnetic turbulence obtained from the four Cluster spacecraft in the terrestrial magnetosheath close to the magnetopause. We show that the turbulence is compressible and dominated by mirror structures, its energy is injected at a large scale kp approximately 0.3 (l approximately 2000 km) via a mirror instability well predicted by linear theory, and cascades nonlinearly and unexpectedly up to kp approximately 3.5 (l approximately 150 km), revealing a new power law in the inertial range not predicted by any turbulence theory, and its strong anisotropy is controlled by the static magnetic field and the magnetopause normal.

Oxygen toxicity in the newborn lung: reversal of inhibition of DNA synthesis in the mouse.

Continuous exposure to 100% oxygen at atmospheric pressure for two weeks causes significant alterations in the growth of the lung and the body of newborn mice. These changes can be divided into three phases. The initial phase, which lasts 96 hours, is characterized by inhibition of lung DNA synthesis, diminished total lung DNA, and a decrease in the ratio of lung DNA to body weight. The intermediate phase from 96 to 144 hours is characterized by a sharp increase in mortality, a plateau in body weight, and a minimal lung DNA/body weight ratio. During this period, however, surviving animals show a reversal of the inhibition of DNA synthesis and thus an increase in total lung DNA. The third phase, occurring after 144 hours, is characterized by a continued increase in DNA synthesis and total lung DNA, a gain in body weight, a return of the lung DNA/body weight ratio to control levels, and a sharp decline in mortality. The survival rate of 54% in newborn mice over two weeks contrasts with the near total mortality reported for adult experimental animals similarly exposed. The reversal of the inhibition of lung DNA synthesis in surviving mice suggests either that some newborn animals are inherently resistant to pulmonary oxygen toxicity or that they develop, during a critical exposure period, an adaptive process necessary for their survival.

The tryptophan synthase from Escherichia coli. An improved purification procedure for the alpha-subunit and binding studies with substrate analogues.

An improved method is described for the purification of the alpha-subunit of tryptophan synthase from Escherichia coli. The standard manganese chloride and acid-precipitation steps have been replaced by rapid and efficient chromatographic procedures. Indoleethanol phosphate, indoleprapanol phosphate and indolebutanol phosphate have been synthesized. They are not cleaved by tryptophan synthase and are strictly competitive inhibitors versus indoleglycerol phosphate. The inhibition constant decreases as the number of methylene groups in the side chain increases. This may reflect an improved accommodation of the indole and phosphate moienerated by binding indole, indoleglycerol phosphate and indolepropanol phosphate to the alpha-subunit are very similar. This reflects the transfer of the indole moiety to an hydrophobic environment within the active center. The binding of indolepropanol phosphate to the alpha2beta2-complex perturbs the spectrum of pyridoxal 5'-phosphate located in the beta2-subunit. This demonstrates direct or indirect interactions between the component active sites. Bind studies by spectrophotometric titration and equilibrium dialysis with indolepropanol [32P]phosphate show that there is only one binding site per equivalent of alpha-subunit. Complex formation with the beta2-subunit increases the affinity of the alpha-subunit for indolepropanol phosphate, It is a general consequence of protein-protein interaction in this system.