Shapes of the U.V. inactivation curves for single and linked double markers in Haemophilus influenzae transforming DNA

The known inverse square law S= 1/(1+CD)², relating survival of transforming activity S to ultraviolet (u.v.) dose D, C being a constant, fails for two linked-double genetic markers in H. influenzae. For these double markers the law is S= 1/(1+CD)⁴, both for u.v. and nitrous acid inactivation. A theoretical model which predicts the inverse square law for singles also predicts the inverse fourth power law for linked doubles, if the possibility of an even number (>0) of genetic recombinations between the markers is allowed for. However, it can be shown rather generally that other models, not specified in exact detail, can lead to the same inverse square law for single markers, and thus to the inverse fourth power law for sufficiently separated linked-doubles. Ability to predict these laws is not, therefore, strong evidence for the validity of any one model. For all these models, the mean number of damaging lesions per unit length of DNA is directly proportional to dose, making (√(1/S)–1) for single markers and (√(1/S)–1) for loosely linked-doubles a reasonable biological measure of inactivating damage in the DNA.     

Durch wasserstoff-transfer induzierte radikal-eliminierungen aus ortho-substituierten benzoesäuremethylestern

The investigation of some ²H-labelled compounds as well as the analysis of energetic properties (appearance potential measurement, kinetic energy release) reveal some unusual elimination of radicals (CH₃^., OH^. resp. CHO^.) from ortho substituted bencoic acid methyl esters. It can be shown that most of the reactions are induced by a novel hydrogen transfer to the carboxyl function.     

Attosecond relative timing jitter and 13 fs tunable pulses from a two-branch Er:fiber laser

We present what is believed to be the first direct measurement of the relative timing jitter between the two parallel pulse trains of a two-branch femtosecond erbium-doped fiber laser, operated without active stabilization. The system provides independently tunable pulses in the near infrared with durations down to 13 fs. Using an interferometric optical cross-correlator, the phase-noise spectral density is measured with high sensitivity in a range from 1 Hz up to the Nyquist frequency of 24.5 MHz. We find an integrated jitter of 11 attoseconds directly after the amplifier stages and 43 as after propagation through free-space optics and nonlinear fibers for frequency conversion.     

Fast wheat variety classification by capillary gel electrophoresis-on-a-chip after single-step one-grain high molecular weight glutenin extraction

Wheat variety identification based on one-step single-grain wheat extraction and fast capillary gel electrophoresis-on-a-chip (CGE-on-a-chip) analyses was evaluated for 15 different wheat varieties grown in Austria. The results of the capillary-based separation system were compared to the internationally accepted method from the International Union for the Protection of New Varieties of Plants which is based on time-consuming sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Comparable protein patterns were observed making the CGE-on-a-chip system a promising tool for high-throughput analysis in food control. For the development of a robust method protein extraction, shelf life of wheat extracts and the instrument’s variability were evaluated. It turned out that a one-step single-grain wheat extraction allowed the sample to be stored at 4 °C for up to 4 weeks without losing any valuable protein information. Furthermore, the technical variation of the whole method is very low making the biological variation of the selected wheat grains the only uncertain factor. Additionally, two unsupervised statistical methods (hierarchical cluster analysis and principal component analysis) were used for variety identification. Identification was successful for a reduced data set of 14 samples from five different wheat varieties making the combination of CGE-on-a-chip analysis of one-step single-grain extraction in combination with automatic data evaluation a promising tool for fast wheat differentiation (within a day).     

Nonlinear quantum optics in a waveguide: distinct single photons strongly interacting at the single atom level

We propose a waveguide-QED system where two single photons of distinct frequency or polarization interact strongly. The system consists of a single ladder-type three level atom coupled to a waveguide. When both optical transitions are coupled strongly to the waveguide's mode, we show that a control photon tuned to the upper transition induces a π phase shift and tunneling of a probe photon tuned to the otherwise reflective lower transition. Furthermore, the system exhibits single photon scattering by a classical control beam. Waveguide-QED schemes could be an alternative to high quality cavities or dense atomic ensembles in quantum information processing.     

All-passive phase locking of a compact Er:fiber laser system

A passively phase-locked laser source based on compact femtosecond Er:fiber technology is introduced. The carrier-envelope offset frequency is set to zero via difference frequency generation between a soliton at a wavelength of 2?μm and a dispersive wave at 860?nm generated in the same highly nonlinear fiber. This process results in a broadband output centered at 1.55?μm. Subsequently, the 40?MHz pulse train seeds a second Er:fiber amplifier, which boosts the pulse energy up to 8?nJ at a duration of 125?fs. Excellent phase stability is demonstrated via f-to-2f spectral interferometry.     

Dynamics of a Strongly Coupled Polaron

We study the dynamics of large polarons described by the Fröhlich Hamiltonian in the limit of strong coupling. The initial conditions are (perturbations of) product states of an electron wave function and a phonon coherent state, as suggested by Pekar. We show that, to leading order on the natural time scale of the problem, the phonon field is stationary and the electron moves according to an effective linear Schrödinger equation.     

On the sum of the index of a parabolic subalgebra and of its nilpotent radical

In this short note, we investigate the following question of Panyushev stated in 2003: ``Is the sum of the index of a parabolic subalgebra of a semisimple Lie algebra and the index of its nilpotent radical always greater than or equal to the rank of ?' Using the formula for the index of parabolic subalgebras conjectured by Tauvel and the author and proved by Fauquant-Millet and Joseph in 2005 and Joseph in 2006, we give a positive answer to this question. Moreover, we also obtain a necessary and sufficient condition for this sum to be equal to the rank of . This provides new examples of direct sum decomposition of a semisimple Lie algebra verifying the ``index additivity condition' as stated by Raïs.