Rekefisket som naturhistorie og samfundssak

1. Trawl fishing for deep sea prawns commenced in Norway in the autumn of 1898 after Hjort had proved in 1897 the existence of great quantities of P. borealis in the fjords of East Norway. On the recommendation of Dr. C. G. JOHS. PETERSEN, HJORT constructed a serviceable gear for this fishery by modifying the Danish eel-seine to an otter-trawl. In table 1 and Figures 2, 3 and 4 a summary is given of the growth of prawn fishing in Norway, Sweden and Denmark. In 1935 nearly 5 million kilogrammes of prawns were fished by these three countries altogether, and 2/3 of this quantity by Norway alone. 2. On the basis of information and charts placed at our disposal, mainly by two fishermen, a survey is given of the prawning grounds which are known from the Svenör Bank to the Trondheim Fjord. 3. The development of gear and fishing craft from HJORT's first trawl and sailing boats to modern gear and motor vessels is described. 4. The statistical value of the prawn fishing in the case of Norway has amounted in recent years to about 2 million kroner per annum. From 1908 to 1935 the value of the total yield in the case of Norway has been more than 22,5 million kroner. The incomes of the fishermen vary considerably according to their ability. Some examples show that in good years the gross income has amounted to about Kr. 20.000,00. The nett income amounts to 35 % - 50 % of the gross. 5. The life history of P. borealis is described on the basis of previous investigations and those undertaken by us. An account is given of the growth of the prawn in Norwegian waters and of the probable number of moultings to which it is subjected. 6. When the prawn fishery commenced an accumulated stock was fished. After the lapse of a number of years the catches became dependent on the annual renewals and the intensity of the fishery. The yield has therefore declined considerably on all the old grounds until in recent years it has become more constant with minor fluctuations. 7. The possibility of discovering new prawn grounds in the Norwegian Channel has been investigated by cruises from the Reef off Kristiansand S. to the waters off Stadt during the summer of 1934. On these cruises it was found that the quantity of prawns declined gradually with the disappearance of detritus from the material of the sea-bed. From Utsira and northwards the bottom consisted of pure sand. 8. Similar experience was gained by BIGELOW and HJORT in the Gulf of Maine (U.S.A.) during the summer of 1936. Quantities of P. borealis capable of being fished on an industrial scale were found in waters which had strong points of resemblance with the prawn grounds in the Norwegian fjords. 9. A comparison between the animal life of the prawn grouncls examined by bottom sampler (BROCH 1935) and that brought up by the trawl shows that the trawl only takes up a very small selection of the bottom fauna, namely, the large forms which live on and over the bottom. A list of the species of fish caught by trawl in Norwegian waters is also given here, and the quantities in which they are takeil. 10. The injurious effects which trawling is said to have on other fisheries are discussed. 11. The effect of the gear on the size of the stock of prawns is examined. 12. The bearing of our investigation is discussed, and recommendations for a minimum mesh in the trawl are made in order to bring the fishery into rational forms and to increase the catches of the fishermen

Imposed quasi-normality in covariance structure analysis

In the analysis of covariance structures, the distance between an observed covariance matrix S of order k x k and C(6) E(S) is minimized by searching over the 8-space. The criterion leading to a best asymptotically normal (BAN) estimator of 0 is found by minimizing the difference between vecS and vecC(6) in a metric that is based on the variance of s. So optimality requires inversion of a k2 x k2 matrix, which is a formidable task when the model contains many equations and the matrix to be inverted is structured insufficiently. The latter can happen when the underlying distribution is non-normal. We present two computationally attractive alternatives that result in estimators for 0 which are approximately BAN. Also, we compare the performance of various weight matrices by means of a Monte-Carlo simulation.

Photodissociation of interstellar N2

Molecular nitrogen is one of the key species in the chemistry of interstellar clouds and protoplanetary disks and the partitioning of nitrogen between N and N2 controls the formation of more complex prebiotic nitrogen-containing species. The aim of this work is to gain a better understanding of the interstellar N2 photodissociation processes based on recent detailed theoretical and experimental work and to provide accurate rates for use in chemical models. We simulated the full high-resolution line-by-line absorption + dissociation spectrum of N2 over the relevant 912-1000 \AA\ wavelength range, by using a quantum-mechanical model which solves the coupled-channels Schr\"odinger equation. The simulated N2 spectra were compared with the absorption spectra of H2, H, CO, and dust to compute photodissociation rates in various radiation fields and shielding functions. The effects of the new rates in interstellar cloud models were illustrated for diffuse and translucent clouds, a dense photon dominated region and a protoplanetary disk.Comment: Online database: http://home.strw.leidenuniv.nl/~ewine/phot

Improved red-response in thin film a-Si:H solar cells with soft-imprinted plasmonic back reflectors

The impact of controlled nanopatterning on the Ag back contact of an n-i-p a-Si:H solar cell was investigated experimentally and through electromagnetic simulation. Compared to a similar reference cell with a flat back contact, we demonstrate an efficiency increase from 4.5% to 6.2%, with a 26% increase in short circuit current density. Spectral response measurements show the majority of the improvement between 600 and 800 nm, with no reduction in photocurrent at wavelengths shorter than 600 nm. Optimization of the pattern aspect ratio using electromagnetic simulation predicts absorption enhancements over 50% at 660 nm

Transient Inactivation of the Medial Prefrontal Cortex Affects Both Anxiety and Decision-Making in Male Wistar Rats

In both humans and rats high levels of anxiety impair decision-making in the Iowa gambling task (IGT) in male subjects. Expression of the immediate early gene c-fos as marker of neural activity in rat studies indicated a role of the medial prefrontal cortex (prelimbic and infralimbic region; mPFC) in mediating the relationship between anxiety and decision-making. To delineate this relationship further and assess the underlying neurobiology in more detail, we inactivated in the present study the mPFC in male rats using a mixture of the GABA-receptor agonists muscimol and baclofen. Rats were exposed to the elevated plus maze (EPM) to measure effects on anxiety and to the rodent version of the IGT (r-IGT). Inactivation led to increased levels of anxiety on the EPM, while not affecting general activity. The effect in the r-IGT (trials 61–120) was dependent on levels of performance prior to inactivation (trial 41–60): inactivation of the mPFC hampered task performance in rats, which already showed a preference for the advantageous option, but not in rats which were still choosing in a random manner. These data suggest that the mPFC becomes more strongly involved as rats have learned task-contingencies, i.e., choose for the best long-term option. Furthermore they suggest, along with the data of our earlier study, that both anxiety and decision-making in rats are mediated through a neural circuitry including at least the mPFC. The data are discussed in relation to recent data of rodent studies on the neural circuitry underlying decision-making

Light trapping in ultrathin plasmonic solar cells

We report on the design, fabrication, and measurement of ultrathin film a-Si:H solar cells with nanostructured plasmonic back contacts, which demonstrate enhanced short circuit current densities compared to cells having flat or randomly textured back contacts. The primary photocurrent enhancement occurs in the spectral range from 550 nm to 800 nm. We use angle-resolved photocurrent spectroscopy to confirm that the enhanced absorption is due to coupling to guided modes supported by the cell. Full-field electromagnetic simulation of the absorption in the active a-Si:H layer agrees well with the experimental results. Furthermore, the nanopatterns were fabricated via an inexpensive, scalable, and precise nanopatterning method. These results should guide design of optimized, non-random nanostructured back reflectors for thin film solar cells