Propagation of sound in turbulent media

Perturbation methods commonly used to study the propagation of acoustic waves in turbulent media are reviewed. Emphasis is on those techniques which are applicable to problems involving long-range propagation in the atmosphere and ocean. Characteristic features of the various methods are illustrated by applying them to particular problems. It is shown that conventional perturbation techniques, such as the Born approximation, yield solutions which contain secular terms, and which therefore have a relatively limited range of validity. In contrast, it is found that solutions obtained with the aid of the Rytov method or the smoothing method do not contain secular terms, and consequently have a much greater range of validity

Joint acceptance for cylinders

Theoretical analysis of response of thin cylindrical shell to random vibratory loadin

Pressure fluctuations due to thin turbulent shear layers

Mean square wall pressure fluctuations in turbulent boundary layer using integral equation

The LDEF ultra heavy cosmic ray experiment

The LDEF Ultra Heavy Cosmic Ray Experiment (UHCRE) used 16 side viewing LDEF trays giving a total geometry factor for high energy cosmic rays of 30 sq m sr. The total exposure factor was 170 sq m sr y. The experiment is based on a modular array of 192 solid state nuclear track detector stacks, mounted in sets of four in 48 pressure vessels. The extended duration of the LDEF mission has resulted in a greatly enhanced potential scientific yield from the UHCRE. Initial scanning results indicate that at least 1800 cosmic ray nuclei with Z greater than 65 were collected, including the world's first statistically significant sample of actinides. Post flight work to date and the current status of the experiment are reviewed

Überlebensfaktoren in der Therapie erblicher Netzhautdegenerationen

Zusammenfassung: In genetisch bedingten Netzhautdystrophien sterben die Photorezeptoren durch Apoptose. Dies ist ein Prozess, dem komplexe molekulare Abläufe zugrunde liegen und der iniziiert wird, wenn proapoptotische Signale in der individuellen Zelle die Oberhand gewinnen. Die Identifizierung der beteiligten Faktoren und deren Wirkungen schuf die Basis dafür, diejenigen mit antiapoptotischem Potenzial in Tiermodellen für vererbte Netzhautdegenerationen auszutesten. Etliche dieser Faktoren waren in der Lage, den Gang der Degeneration zu verlangsamen. Ein Aufhalten oder gar ein Verhindern des Krankheitsverlaufs ist jedoch bis dato nicht realisiert. Zudem zeigte sich, dass der Erhalt der Morphologie nicht mit dem Erhalt der Funktion im ERG korrelieren muss. Vertiefte Einsichten in die pro- und antiapoptotischen Netzwerke sind klar vonnöten, damit antiapoptotische Therapien mit Überlebensfaktoren den Weg zur Applikation beim Menschen finden. Im Vergleich dazu konnte in einem Hundemodell für Leber-Amaurose durch elektive Gentherapie die retinale Funktion hergestellt und somit der Nachweis der Wirksamkeit der Methode erbracht werde

Progress report on the ultra heavy cosmic ray experiment (AO178)

The Ultra Heavy Cosmic Ray Experiment (UHCRE) is based on a modular array of 192 side-viewing solid state nuclear track detector stacks. These stacks were mounted in sets of four in 48 pressure vessels employing sixteen peripheral Long Duration Exposure Facility (LDEF) trays. The extended duration of the LDEF mission has resulted in a greatly enhanced scientific yield from the UHCRE. The geometry factor for high energy cosmic ray nuclei, allowing for Earth shadowing, was 30 sq m-sr, giving a total exposure factor of 170 sq m-sr-y at an orbital inclination of 28.4 degrees. Scanning results indicate that about 3000 cosmic ray nuclei in the charge region with Z greater than 65 were collected. This sample is more than ten times the current world data in the field (taken to be the data set from the HEAO-3 mission plus that from the Ariel-6 mission) and is sufficient to provide the world's first statistically significant sample of actinide (Z greater than 88) cosmic rays. Results to date are presented including details of ultra-heavy cosmic ray nuclei, analysis of pre-flight and post-flight calibration events and details of track response in the context of detector temperature history. The integrated effect of all temperature and age related latent track variations cause a maximum charge shift of +/- 0.8 e for uranium and +/- 0.6 e for the platinum-lead group. The precision of charge assignment as a function of energy is derived and evidence for remarkably good charge resolution achieved in the UHCRE is considered. Astrophysical implications of the UHCRE charge spectrum are discussed

Testing for Markovian Character and Modeling of Intermittency in Solar Wind Turbulence

We present results of statistical analysis of solar wind turbulence using an approach based on the theory of Markov processes. It is shown that the Chapman-Kolmogorov equation is approximately satisfied for the turbulent cascade. We evaluate the first two Kramers-Moyal coefficients from experimental data and show that the solution of the resulting Fokker-Planck equation agrees well with experimental probability distributions. Our results suggest the presence of a local transfer mechanism for magnetic field fluctuations in solar wind turbulence

Raman solitons in transient SRS

We report the observation of Raman solitons on numerical simulations of transient stimulated Raman scattering (TSRS) with small group velocity dispersion. The theory proceeds with the inverse scattering transform (IST) for initial-boundary value problems and it is shown that the explicit theoretical solution obtained by IST for a semi-infinite medium fits strikingly well the numerical solution for a finite medium. We understand this from the rapid decrease of the medium dynamical variable (the potential of the scattering theory). The spectral transform reflection coefficient can be computed directly from the values of the input and output fields and this allows to see the generation of the Raman solitons from the numerical solution. We confirm the presence of these nonlinear modes in the medium dynamical variable by the use of a discrete spectral analysis.Comment: LaTex file, to appear in Inverse Problem