93 research outputs found
Teil (A): Experimentelle Untersuchungen zur Simulation einer natuerlichen Erdgrenzschicht im Windkanal. Von W. Frank. Teil (B): Systematische Untersuchungen zur Bestimmung fluktuierender Druecke an einem Gebaeudemodell. Von W. Frank und M. Lettmann
No full textOrigin and fate of the secondary nitrite maximum in the Arabian Sea
No full textThe Arabian Sea harbours one of the three major oxygen minimum zones (OMZs) in the world's oceans, and it alone is estimated to account for ~10–20 % of global oceanic nitrogen (N) loss. While actual rate measurements have been few, the consistently high accumulation of nitrite (NO2?) coinciding with suboxic conditions in the central-northeastern part of the Arabian Sea has led to the general belief that this is the region where active N-loss takes place. Most subsequent field studies on N-loss have thus been drawn almost exclusively to the central-NE. However, a recent study measured only low to undetectable N-loss activities in this region, compared to orders of magnitude higher rates measured towards the Omani Shelf where little NO2? accumulated (Jensen et al., 2011). In this paper, we further explore this discrepancy by comparing the NO2?-producing and consuming processes, and examining the relationship between the overall NO2? balance and active N-loss in the Arabian Sea. Based on a combination of 15N-incubation experiments, functional gene expression analyses, nutrient profiling and flux modeling, our results showed that NO2? accumulated in the central-NE Arabian Sea due to a net production via primarily active nitrate (NO3?) reduction and to a certain extent ammonia oxidation. Meanwhile, NO2? consumption via anammox, denitrification and dissimilatory nitrate/nitrite reduction to ammonium (NH4+) were hardly detectable in this region, though some loss to NO2? oxidation was predicted from modeled NO3? changes. No significant correlation was found between NO2? and N-loss rates (p>0.05). This discrepancy between NO2? accumulation and lack of active N-loss in the central-NE Arabian Sea is best explained by the deficiency of labile organic matter that is directly needed for further NO2? reduction to N2O, N2 and NH4+, and indirectly for the remineralized NH4+ required by anammox. Altogether, our data do not support the long-held view that NO2? accumulation is a direct activity indicator of N-loss in the Arabian Sea or other OMZs. Instead, NO2? accumulation more likely corresponds to long-term integrated N-loss that has passed the prime of high and/or consistent in situ activities
Compton polarimetry with a 36-fold segmented HPGe-detector of the AGATA-type
No full textThe calibration of a highly-segmented AGATA-type HPGe-detector as a γ-ray Compton polarimeter and a method for (quasi-)continuous angle Compton polarimetry are presented. The high granularity, combined with the large detection efficiency of the AGATA-type HPGe-crystals, offers a significant advantage for polarization measurements of γ-radiation. A polarization-directional correlation experiment with γ-rays from a 60Co source with an activity of about 680 kBq was used to determine the polarization sensitivity of a single AGATA-type HPGe-crystal at 1173 and 1332 keV and to demonstrate the method. The polarization measurement was based on segment information. In our set-up a polarization sensitivity of 19% at 1332 keV has been achieved
Lettmann (Birth, 1881-02-09)
No full textAddress: 582 Freeman976/Pg 91/1881/M W/U.S./Ger./Mrs. Buether, Mid.Original record filed in drawer labeled 'Leonhard-Lewis, P'
Lettmann, Albert (Birth, 1886-05-28)
No full textAddress: 38 - 15th St.3321/Pg 156/1886/M W/Cinti O/Cinti.O./Mrs Buecker, MidOriginal record filed in drawer labeled 'Leonhard-Lewis, P'
Lettmann, Fred (Death, 1907-11-08)
No full textAddress: Libert & Dudley 1402 W. LibertyAge at death: 64151/Pg 121/1907/M W W/Germany/Otis L. Cameron, Coroner/Busse & Borgmann RaschigsOriginal record filed in drawer labeled 'Leonhard-Lewis, P'
Triaxiality of neutron-rich Ge 84,86,88 from low-energy nuclear spectra
No full textM. Lettmann et al. -- 6 pags., 5 figs., tab.γ-ray transitions between low-spin states of the neutron-rich Ge84,86,88 were measured by means of in-flight γ-ray spectroscopy at 270 MeV/u. Excited 61+,41,2+, and 21,2+ states of Ge84,86 and 41+ and 21,2+ states of Ge88 were observed. Furthermore, a candidate for a 31+ state of Ge86 was identified. This state plays a key role in the discussion of ground-state triaxiality of Ge86, along with other features of its low-energy level scheme. A new region of triaxially deformed nuclei is proposed in the Ge isotopic chain.We acknowledge support from the German
BMBF Grants No. 05P15RDFN1, No. 05P12RDFN8, and No.
05P15PKFNA; ERC Grant No. MINOS-258567; the Spanish
Ministerio de Economía y Competitividad under Contracts
No. FPA2014-57196-C5-4-P and No. FIS-2014-53434, the
Vietnam Ministry of Science and Technology, as well as from
the Science and Technology Facilities Council (STFC). We
further thank GSI for providing computing facilitiesPeer Reviewe
Clausal Analysis of First-order Proof Schemata
No full textProof schemata are a variant of LK-proofs able to simulate various induction
schemes in first-order logic by adding so called proof links to the standard
first-order LK-calculus. Proof links allow proofs to reference proofs thus
giving proof schemata a recursive structure. Unfortunately, applying reductive
cut- elimination is non-trivial in the presence of proof links. Borrowing the
concept of lazy instantiation from functional programming, we evaluate proof
links locally allowing reductive cut-elimination to proceed past them. Though,
this method cannot be used to obtain cut-free proof schemata, we nonetheless
obtain important results concerning the schematic CERES method, that is a
method of cut-elimination for proof schemata based on resolution. In "Towards a
clausal analysis of cut-elimination", it was shown that reductive
cut-elimination transforms a given LK-proof in such a way that a subsumption
relation holds between the pre- and post-transformation characteristic clause
sets, i.e. the clause set representing the cut-structure of an LK-proof. Let
CL(A') be the characteristic clause set of a normal form A' of an LK-proof A
that is reached by performing reductive cut-elimination on A without atomic cut
elimination. Then CL(A') is subsumed by all characteristic clause sets
extractable from any application of reductive cut-elimination to A. Such a
normal form is referred to as an ACNF top and plays an essential role in
methods of cut-elimination by resolution. These results can be extended to
proof schemata through our "lazy instantiation" of proof links, and provides an
essential step toward a complete cut-elimination method for proof schemata.Comment: Submitted to LPAR 2017. Pre-prin
A note on ocean surface drift with application to surface velocities measured with HF Radar
No full textThe ocean drift current consists of a (local) pure drift current generated by the interaction of wind and waves at the sea surface, to which the surface geostrophic current is added vectorially. We present (a) a similarity solution for the wave boundary layer (which has been validated through the prediction of the 10-m drag law), from which the component of pure drift current along the direction of the wind (and hence the speed factor) can be evaluated from the 10-m wind speed and the peak wave period, and (b) a similarity solution for the Ekman layers of the two fluids, which shows that under steady-state neutral conditions the pure drift current lies along the direction of the geostrophic wind, and has a magnitude 0.034 that of the geostrophic wind speed. The co-existence of these two similarity solutions indicates that the frictional properties of the coupled air-sea system are easily evaluated functions of the 10-m wind speed and the peak wave period, and also leads to a simple expression for the angle of deflection of the pure drift current to the 10 m wind. The analysis provides a dynamical model for global ocean drift on monthly and annual time scales for which the steady-state neutral model is a good approximation. In particular, the theoretical results appear to be able to successfully predict the mean surface drift measured by HF Radar, which at present is the best technique for studying the near surface velocity profile
On the variability of the Charnock constant and the functional dependence of the drag coefficient on wind speed: Part II-Observations
No full textAn analytical expression for the 10 m drag law in terms of the 10 m wind speed at the maximum in the 10 m drag coefficient, and the Charnock constant is presented, which is based on the results obtained from a model of the air-sea interface derived in Bye et al. (2010). This drag law is almost independent of wave age and over the mid-range of wind speeds (5−17 ms−1) is very similar to the drag law based on observed data presented in Foreman and Emeis (2010). The linear fit of the observed data which incorporates a constant into the traditional definition of the drag coefficient is shown to arise to first-order as a consequence of the momentum exchange across the air-sea boundary layer brought about by wave generation and spray production which are explicitly represented in the theoretical model
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