Zur Frage einer „dynamischen“ Prüfung von Magnetkompassen

Zusammenfassung Magnetkompasse auf durch Seegang bewegten Schiffen können Dauerauslenkungen aufweisen. Nach kurzer Erläuterung des Problems werden die Einrichtungen und Hilfsmittel zur Durchführung der dynamischen Prüfung von Magnetkompassen beschrieben, vorläufige Prüfungsergebnisse mitgeteilt und die sich daraus ergebenden Schlußfolgerungen gezogen.

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On the problem of a dynamical testing of magnetic compasses

Summary Magnetic compasses on board of ships subjected to the motion of the sea are often liable to continuous deviations. After a short discussion of the problem, the installations and the aids in use for the performance of the dynamic investigations of magnetic compasses are described, preliminary results of the investigations are communicated and the conclusions arising from them are drawn.

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Sur le problème d'une vérification »dynamique« des compas magnétiques

Résumé Des compas magnétiques à bord de bâtiments soumis aux mouvements de la mer subissent souvent des déviations permanentes. Après un bref exposé de ce problème on décrit les dispositifs et les moyens auxiliaires en usage pour l'examen dynamique de compas magnétiques; de plus, on en communique les résultats préliminaires et on tire les conclusions qui en découlent.

     

Taphonomic phenomenon of ancient hair from Glacial Beringia: perspectives for palaeoecological reconstructions

An accumulation of mammoth hair, discovered in the Bol'shaya Chukochya River valley (northeast Yakutia, Russia), was found to contain remains of terrestrial and aquatic organisms, including plants, insects, crustaceans, birds and mammals. Radiocarbon dating indicated that this post‐mortem taphocoenosis represented multiple time periods. The mammoth hair was dated to older than 45 ka BP, the plants were dated to 12 750±50 a BP (which corresponds to a shift in the environmental conditions and landscapes during the formation of thermokarst in northeastern Russia) and the bird feathers were dated to 4115±40 a BP. A scenario of the formation of this fossil assemblage is proposed, covering the MIS 3‐1 time range. The hair also yielded various Arctic branchiopod crustaceans, which inhabit shallow temporary water bodies and therefore are important for reconstruction of palaeoenvironments. The cladoceran subgenus Daphnia (Ctenodaphnia), currently absent from the Asian part of Beringia, is reported from this region for the first time. The study demonstrates that the discovered permafrost‐preserved hair is a unique repository of Ice Age organisms.     

Interplay between scintillation and ionization in liquid xenon Dark Matter searches

We provide a new way of constraining the relative scintillation efficiency L_eff for liquid xenon. Using a simple estimate for the electronic and nuclear stopping powers together with an analysis of recombination processes we predict both the ionization and the scintillation yields. Using presently available data for the ionization yield, we can use the correlation between these two quantities to constrain L_eff from below. Moreover, we argue that more reliable data on the ionization yield would allow to verify our assumptions on the atomic cross sections and to predict the value of L_eff. We conclude that the relative scintillation efficiency should not decrease at low nuclear recoil energies, which has important consequences for the robustness of exclusion limits for low WIMP masses in liquid xenon Dark Matter searches.     

Establishment of “Zernov’s Phyllophora field” marine reserve: Protection and restoration of a unique ecosystem

“Zernov’s Phyllophora field” is a unique habitat located in the northwestern Black Sea. At the site, there is a dense stand of agarophytes (red algae) and a high diversity of associated fauna. On November 21 2008, the president of Ukraine (Victor Yuschenko) declared this area a botanical reserve of state-wide importance; it was established to protect and restore a unique natural environment. “Zernov’s Phyllophora field” is the first offshore, fully marine MPA in the Black Sea, and it is the largest. The total area is 402,500 ha, covering 12.5% of the northwestern shelf of the Black Sea. The Ukrainian Scientific Centre for the Ecology of Sea has developed a program for (1) preservation, (2) restoration and (3) further rational use of biological resources at the site. It contains three conforming and interdependent sub-programs that put forward a series of measures for implementing the objectives (preservation, restoration, sustainable resource use).The northwestern Black Sea was heavily impacted by anthropogenic loading in the period 1970–1980, and Zernov’s Phyllophora field was considerably degraded and reduced in area. During recent years the perimeter of the Phyllophora field has slightly extended, and restoration of the benthic phytocoenosis has begun. Assigning this area the status of a marine reserve (Marine Protected Area) will further promote processes of restoring faunal and floristic biodiversity to historically healthy levels.     

Radio continuum surveys

The Rhodes University radio astronomy group has been involved in radio continuum mapping of southern extended radio sources since 1976. We describe the various mapping projects undertaken with the HartRAO telescope, particularly the Rhodes/HartRAO 2300 MHz all-sky survey, and speculate on future projects.     

The Rhodes/HartRAO 2326-MHz radio continuum survey

We have made scanning observations with the HartRAO 26-m radio telescope to obtain a pencil-beam map of 67 per cent of the sky at 2326 MHz. This is the highest resolution and highest frequency radio continuum map of this type made of such a large area of sky.   In this paper we describe the observations and data reduction procedures used to produce the survey. The resulting map has an angular resolution (HPBW) of 20 arcmin, and the rms pointing accuracy is 1.2 arcmin. The rms noise fluctuations are less than 30-mK T _FB over the whole map. We estimate that the uncertainty in the temperature scale is less than 5 per cent, and that the error in the absolute zero level is better than 80-mK T _FB in any direction.   High-contrast half-tone images of the data with a model of the diffuse galactic background subtracted are presented. These images show many complex emission structures up to and beyond 50° latitude, and illustrate the quality of the data. Extracts from the survey data are available via FTP by arrangement with the authors.     

Statistical analysis of vitrinite reflectance data—a new approach

The reflectance of vitrinite (collotelinite) particles is a widely used parameter as a geothermometer for the estimation of the thermal maturity of organic matter enclosed in rocks. However, several problems have occurred during the last decades, which can be traced back to basically three causes: human mistakes, technical problems, and problems associated with the structural and compositional inhomogeneity of organic matter. Whilst in most cases the first two types of uncertainties can be handled by standardization, the third can cause significant problems during interpretation due to its generally inestimable character. The suppression of vitrinite reflectance and statistical problems originated from small sample size, and outliers belong to this latter type.International standards, such as the ASTM and the ISO, define the vitrinite reflectance parameter as a statistical average of measured data, disregarding the fact that the average is an unresisting and unrobust statistical parameter. In other words, the average is very sensitive to outliers and distribution.The aim of this research was to find and test a better, more resistant, and robust statistical parameter used by traditional parametric and nonparametric statistics, which can be applied in practice instead of the average. Three categories of statistical problems were studied on coal and disperse organic matter (DOM) samples: the distribution of measured values, the effect of data number, and the effect of outliers on statistical parameters. The statistical experiments carried out on numerous original and generated sample sets show that the median (med) and the most frequent value (Mn), a special weighted average, are better parameters to estimate the thermal maturity of organic matter especially above 1% reflectance value.     

Research Note: First results of a low‐altitude unmanned aircraft system gamma survey by comparison with the terrestrial and aerial gamma survey data

In order to increase the efficiency of geological survey in difficult landscape‐morphological conditions, the authors have developed low‐altitude gamma technology surveys based on a multi‐rotor unmanned aircraft system, also known informally as Drones. These results have been compared against those from standard terrestrial and aerial gamma surveys. The successful results obtained at the reference site show that the developed methodology enables compilation of high‐quality data in difficult landscape conditions. These results yield the same level of information content as standard terrestrial gamma surveys. The exact unmanned aircraft system altitude over the earth must be maintained for carrying out high‐quality surveys. It was found that a CsI(Tl) detector with sizes 80 × 80 mm (vol. 0.4 dm³) enables obtaining of high‐quality radiometric data at altitudes of up to 70 m, at a speed of at least 20 km/h. The authors believe that low altitude ‘quasi‐terrestrial’ gamma surveys with a terrain drape may in the future replace terrestrial gamma surveys since they can offer better effectiveness at a lower cost.     

Forward–backward scheme on the B/E grid modified to suppress lattice separation: the two versions, and any impact of the choice made?

Ever since its introduction to meteorology in the early 1970s, the forward–backward scheme has proven to be a very efficient method of treating gravity waves, with an added bonus of avoiding the time computational mode of the leapfrog scheme. It has been and it is used today in a number of models. When used on a square grid other than the Arakawa C grid, modification is or modifications are available to suppress the noise-generating separation of solutions on elementary C grids. Yet, in spite of a number of papers addressing the scheme and its modification, or modifications, issues remain that have either not been addressed or have been commented upon in a misleading or even in an incorrect way. Specifically, restricting ourselves to the B/E grid does it matter and if so how which of the two equations, momentum and the continuity equation, is integrated forward? Is there just one modification suppressing the separation of solutions, or have there been proposed two modification schemes? Questions made are addressed and a number of misleading statements made are recalled and commented upon. In particular, it is demonstrated that there is no added computational cost in integrating the momentum equation forward, and it is pointed out that this would seem advantageous given the height perturbations excited in the first step following a perturbation at a single height point. Yet, 48-h numerical experiments with a full-physics model show only a barely visible difference between the forecasts done using one and the other equation forward.     

Über die Entwicklung magnetischer Fernkompasse in Deutschland

Zusammenfassung Es werden die Umstände angegeben, die für die Entwicklung von magnetischen Fernkompassen maßgebend waren, und die Forderungen erwähnt, denen solche Geräte genügen müssen. Zwei Haupttypen lassen sich unterscheiden: der primäre, der die für die Betätigung von Anzeigeinstrumenten notwendigen Meßgrößen (z. B. elektr. Spannungen) aus dem magnetischen Erdfeld direkt gewinnt, und der sekundäre, bei dem diese Meßgrößen auf dem Wege über ein Magnetnadelsystem erzeugt, in verschiedener Weise umgeformt und auf Tochterkompasse übertragen werden.Aus der Vielfalt der in Deutschland entwickelten Geräte werden Aufbau und Wirkungsweise einer Reihe typischer Konstruktionen näher beschrieben; ihre speziellen Vorzüge und Nachteile werden besprochen.

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On the development of magnetic telecompasses in Germany

Summary The author describes the conditions which have decisively influenced the development of magnetic telecompasses and states the demands such instruments have to meet. The telecompasses may be divided into two categories, viz: The direct compass which directly receives the quantities to be measured (e. g. electrial voltages) which are necessary for operating the indicating or repeater instruments from the earth's magnetic field and the indirect compass in which these quantities are produced by the aid of a system of magnetic needles and transformed in different ways in order to be finally transmitted to the repeater compasses.From the many types of magnetic telecompasses developed in Germany a number of typical constructions is described in detail and their special advantages and deficiencies are discussed.

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Sur les systèmes de télécompas magnétiques développés en Allemagne

Résumé L'auteur décrit les circonstances qui ont décisivement influencé le développement des télécompas magnétiques et traite les besoins auxquels ces appareils doivent répondre. Les télécompas se répartissent en deux types principaux: Le type direct qui reçoit immédiatement du champ magnétique terrestre les valeurs à mesurer (p. e. les tensions électriques) nécessaires pour la mise en fonction des compas indicateurs, et le type indirect qui est muni d'un système d'aiguilles magnétiques pour la production de ces valeurs qui sont transmises aux compas répétiteurs après avoir été transformées de manières différentes.De la multiplicité des télécompas développés en Allemagne quelques constructions typiques sont choisies dont on précise la structure et le fonctionnement et expose les avantages ainsi que les inconvénients particuliers.