A laser-diode-pumped acoustic-optic Q-switched Nd:YVO4 slab laser with a hybrid resonator

A 32.1 W laser-diode-stack pumped acoustic-optic Q-switched Nd:YVO4 slab laser with hybrid resonator at 1064 nm was demonstrated with the pumping power of 112 W and repetition rate of 40 kHz, the pulse duration was 32.47 ns. The slope efficiency and optical-to-optical efficiency were 37 and 28.7%, respectively. At the repetition rate of 20 kHz and pumping power of 90 W, the average output power and pulse duration were 20.4 W and 20.43 ns, respectively. With the pumping power of 112 W, the beam quality M-2 factors in CW operation were measured to be 1.3 in stable direction and 1.6 in unstable direction.

Über die Herkunft des starken Kabeljau-Jahrgangs 1996 in der Nordsee

Cod in the North Sea is expected to reach „Safe biological limit“ due to a strong 1996 year-class. The cod fry was seen first as 5 cm fingerlings in the catches during a hydroacoustic survey in the southeastern North Sea. Back-calculations of the water drift show with high probability that the respective spawning ground was situated in the southwestern North Sea.

Multiterawatt laser system based on optical parametric chirped pulse amplification

A compact multiterawatt laser system based on optical parametric chirped pulse amplification is demonstrated. Chirped pulses are amplified from 20 pJ to 900 mJ by two lithium triborate optical parametric preamplifiers and a final KDP optical parametric power amplifier with a pump energy of 5 J at 532 nm from Nd:YAG-Nd: glass hybrid amplifiers, After compression, we obtained a final output of 570-mJ-155-fs pulses with a peak power of 3.67 TW, which is the highest output power from an optical parametric chirped pulse amplification laser, to the best of our knowledge. (C) 2002 Optical Society of America.

Further acceleration of MeV electrons by a relativistic laser pulse

With the development of photocathode rf electron gun, electrons with high-brightness and mono-energy can be obtained easily. By numerically solving the relativistic equations of motion of an electron generated from this facility in laser fields modelled by a circular polarized Gaussian laser pulse, we find the electron can obtain high energy gain from the laser pulse. The corresponding acceleration distance for this electron driven by the ascending part of the laser pulse is much longer than the Rayleigh length, and the light amplitude experienced on the electron is very weak when the laser pulse overtakes the electron. The electron is accelerated effectively and the deceleration can be neglected. For intensities around 10(19) W(.)mu m(2)/cm(2), an electron's energy gain near 0.1 GeV can be realized when its initial energy is 4.5 MeV, and the final velocity of the energetic electron is parallel with the propagation axis. The energy gain can be up to 1 GeV if the intensity is about 10(21) W(.)mu m(2)/cm(2). The final energy gain of the electron as a function of its initial conditions and the parameters of the laser beam has also been discussed.

Keine Erholung der westgrönländischen Grundfischbestände

Since 1991, the aggregate biomass of fish stocks inhabiting the West Greenland shelf stagnates at the lowest level. The latest survey results of cruise no. 152 conducted by FRV 'Walther Herwig III' do not indicate any improvements in state of the stocks, although no fishing effort was recently directed towards groundfish. The cod stock showed again a record low and is presently dominated by recruits of the year classes 1991 and 1993. Both year classes are considered to be weak and the cod stock is beyond the 'minimum biologically acceptable level'. Consequently, an increase in stock abundance is not expected either in short or long term. Other ecologically or economically important fish species, American plaice, redfish, wolffish and starry skate, were also found to have minimum stock abundances. By-catch estimates of juvenile groundfish taken by the shrimp fishery, operating at traditional grounds of cod and redfish fisheries, are indispensible. Analysis of climatological data from Nuuk/West Greenland indicates that climate during the past fourty years was characterized by two decades of anomalous warm conditions, and cooling which dominates the dimate since 1969. Anomalous cold events were encountered during 1983, 1984 and during 1992, 1993. Similar to the air temperature anomalies, autumn temperatures of the ocean surface layer indicate cold and warm periods during the past thirty years. In contrast to the colder than normal atmospheric conditions during the early nineties, however, the ocean conditions indicate intermediate warming.

Accurate determination of the absolute phase and temporal-pulse phase of few-cycle laser pulses

A Fourier analysis method is used to accurately determine not only the absolute phase but also the temporal-pulse phase of an isolated few-cycle (chirped) laser pulse. This method is independent of the pulse shape and can fully characterize the light wave even though only a few samples per optical cycle are available. It paves the way for investigating the absolute phase-dependent extreme nonlinear optics, and the evolutions of the absolute phase and the temporal-pulse phase of few-cycle laser pulses.

Nachwuchsprobleme bei Nordseegarnelen?

Die Nordseegarnele (Crangon crangon), im Handel auch einfach "Krabbe" genannt, ist eines der wichtigsten Fangobjekte unserer Fischerei. Da die Garnelen einer weitgehend örtlich gebundenen, nationalen Fischerei unterliegen, stehen sie nicht im Mittelpunkt des Interesses der EG-Fischereipolitik. Sie unterliegen keinerlei Quotenregelung und sind damit auch nicht Gegenstand politischer Verhandlungen.

Feeding of Gammarus lacustris Sars under different conditions of habitation [Translation from: [Trophic relations of freshwater invertebrates.] (ed. G. G. Vinberg) pp.94-98. Leningrad, Zool.Inst.AN SSSR, 1980]

The amphipod Gammarus lacustris, a regular representative of lacustrine communities, often plays a significant role in the transformation of matter and energy. The object of the present work was to clarify the quantitative side of the feeding of the amphipod under different conditions of habitation. Experimental works on determination of the rate of consumption of food and its dependence on body-weight were carried out in the summer periods 1975-1978 on three water-bodies of the Krasnoyarsk region, of different conditions of habitation for the amphipods.

Generación combinada a partir de biogás de calor y electricidad

[ES]El análisis y la resolución de casos prácticos engloban la resolución de casos prácticos, el análisis de las alternativas posibles o la resolución de casos concretos. En este trabajo se pretende analizar y resolver un caso concreto, de un proceso de producción de hidrógeno. Una vez expuesto el contexto y el análisis de las alternativas, se procederá a explicar el proceso de obtención y aprovechamiento del hidrógeno. El hidrógeno, se obtendrá a partir de la gasificación d la biomasa. Una vez se haya obtenido la corriente de hidrógeno, esta alimentará a una pila de alta temperatura tipo SOFC, para obtener generación combinada de calor y electricidad.

Anomalous electric dipole internal conversion

Electric dipole internal conversion has been experimentally studied for several nuclei in the rare earth region. Anomalies in the conversion process have been interpreted in terms of nuclear structure effects. It was found that all the experimental results could be interpreted in terms of the j ∙ r type of penetration matrix element; the j ∙ ∇ type of penetration matrix element was not important. The ratio λ of the El j ∙ r penetration matrix element to the El gamma-ray matrix element was determined from the experiments to be:

Lu¹⁷⁵,396 keV, λ = - 1000 ± 100;

282 keV, λ = 500 ± 100;

144 keV, λ = 500 ± 250;

Hf¹⁷⁷, 321 keV λ = - 1400 ± 200;

208 keV λ = - 90 ± 40;

72 keV |λ| ≤ 650;

Gd¹⁵⁵, 86 keV λ = - 150 ± 100;

Tm¹⁶⁹, 63 keV λ = - 100 ± 100;

W¹⁸², 152 keV, λ = - 160 ±80;

67 keV, λ = - 100 ± 100.

Predictions for λ are made using the unified nuclear model.