Nonperturbative analysis of coupled quantum dots in a phonon bath

Transport through coupled quantum dots in a phonon bath is studied using the recently developed real-time renormalization-group method. Thereby, the problem can be treated beyond perturbation theory regarding the complete interaction. A reliable solution for the stationary tunnel current is obtained for the case of moderately strong couplings of the dots to the leads and to the phonon bath. Any other parameter is arbitrary, and the complete electron-phonon interaction is taken into account. Experimental results are quantitatively reproduced by taking into account a finite extension of the wavefunctions within the dots. Its dependence on the energy difference between the dots is derived.Comment: 8 pages, 6 figure

Image segmentation by graph partitioning

In this paper we propose an hybrid method for the image segmentation which combines the edge-based, region-based and the morphological techniques in conjunction through the spectral based clustering approach. An initial partitioning of the image into atomic regions is set by applying a watershed method to the image gradient magnitude. This initial partition is the input to a computationally efficient region segmentation process which produces the final segmentation. We have applied our approach on several images of the Berkeley Segmentation Dataset. The results reveal the accuracy of the propose method

Polymer-based controlled-release fed-batch microtiter plate - diminishing the gap between early process development and production conditions

Background: Fed-batch conditions are advantageous for industrial cultivations as they avoid unfavorable phenomena appearing in batch cultivations. Those are for example the formation of overflow metabolites, catabolite repression, oxygen limitation or inhibition due to elevated osmotic concentrations. For both, the early bioprocess development and the optimization of existing bioprocesses, small-scale reaction vessels are applied to ensure high throughput, low costs and prompt results. However, most conventional small-scale procedures work in batch operation mode, which stands in contrast to fed-batch conditions in large-scale bioprocesses. Extensive expenditure for installations and operation accompany almost all cultivation systems in the market allowing fed-batch conditions in small-scale. An alternative, more cost efficient enzymatic glucose release system is strongly influenced by environmental conditions. To overcome these issues, this study investigates a polymer-based fed-batch system for controlled substrate release in microtiter plates. Results: Immobilizing a solid silicone matrix with embedded glucose crystals at the bottom of each well of a microtiter plate is a suitable technique for implementing fed-batch conditions in microtiter plates. The results showed that the glucose release rate depends on the osmotic concentration, the pH and the temperature of the medium. Moreover, the applied nitrogen source proved to influence the glucose release rate. A new developed mathematical tool predicts the glucose release for various media conditions. The two model organisms E. coli and H. polymorpha were cultivated in the fed-batch microtiter plate to investigate the general applicability for microbial systems. Online monitoring of the oxygen transfer rate and offline analysis of substrate, product, biomass and pH confirmed that fed-batch conditions are comparable to large-scale cultivations. Furthermore, due to fed-batch conditions in microtiter plates, product formation could be enhanced by the factor 245 compared to batch cultivations. Conclusions: The polymer-based fed-batch microtiter plate represents a sophisticated and cost efficient system to mimic typical industrial fed-batch conditions in small-scale. Thus, a more reliable strain screening and early process development can be performed. A systematical scale-down with low expenditure of work, time and money is possible. © 2019 The Author(s)

Apollo 15 rake sample microbreccias and non-mare rocks: Bulk rock, mineral and glass electron microprobe analyses

Quantitative electron microprobe data of Apollo 15 nonmare rake samples are presented. Bulk analyses of lithic fragments in the nomare rocks (expressed in oxide weight-percent) and the corresponding CIPW molecular norms are given. The mineralogy of the rocks and lithic fragments are also given; structural formulae for complete analyses and molecular end-members for all mineral analyses are included. The mineral analyses include pyroxene, olivine, plagioclase, barian K-feldspar, spinel and ilmenite, cobaltian metallic nickel-iron as well as SiO2-K2O-rich residual glass. Electron micropobe analyses (oxide weight percent) of glasses in loose fines and microbreccia samples and their CIPW molecular norms are presented along with electron microprobe data on bulk, mineral, and matrix glass from chondrules

Classificational parameters for acapulcoites and lodranites: The cases of FRO 90011, EET 84302 and ALH A81187/84190

Acapulcoites and lodranites probably sample a common parent body, which has experienced a range of partial melting. We present classificational parameters which allow acapulcoites-lodranites to be distinguished from other groups of meteorites, as well as from each other. Petrography can complement oxygen isotopic compositions in separating these meteorites from other groups of stony-irons and primitive achondrites, while petrographic properties alone distinguish acapulcoites from lodranites. Acapulcoites differ from lodranites in having smaller grain sizes, abundant Fe, Ni-FeS as micron-sized veins and plagioclase which escaped melting. We have applied these criteria to three new members of the group. FRO 90011 is a typical lodranite; EET 84302 is intermediate in many properties between acapulcoites and lodranites; and ALH A81187/84190 are paired meteorites and are first low-FeO acapulcoites. These meteorites provide a wider spectrum of samples from the acapulcoite-lodranite parent body and suggests that this body may have had a complex structure

NP-hardness of the cluster minimization problem revisited

The computational complexity of the "cluster minimization problem" is revisited [L. T. Wille and J. Vennik, J. Phys. A 18, L419 (1985)]. It is argued that the original NP-hardness proof does not apply to pairwise potentials of physical interest, such as those that depend on the geometric distance between the particles. A geometric analog of the original problem is formulated, and a new proof for such potentials is provided by polynomial time transformation from the independent set problem for unit disk graphs. Limitations of this formulation are pointed out, and new subproblems that bear more direct consequences to the numerical study of clusters are suggested.Comment: 8 pages, 2 figures, accepted to J. Phys. A: Math. and Ge

Forest investigations by polarimetric AIRSAR data in the Harz mountains

The Harz Mountains in the North of Germany have been a study site for several remote sensing investigations since 1985, as the mountainous area is one of the forest regions in Germany heavily affected by forest decline, especially in the high altitudes above 800 m. In a research program at the University of Berlin, methods are developed for improving remote sensing assessment of forest structure and forest state by additional GIS information, using several datasets for establishing a forest information system. The Harz has been defined as a test site for the SIR-C/X-SAR mission which is going to deliver multifrequency and multipolarizational SAR data from orbit. In a pilot project let by DLR-DFD, these data are to be investigated for forestry and ecology purposes. In preparing a flight campaign to the SIR-C / X-SAR mission, 'MAC EUROPE 1991', performed by NASA/JPL, an area of about 12 km in the Northern Harz was covered with multipolarizational AIRSAR data in the C-, L- and P-band, including the Brocken, the highest mountain of the Harz, with an altitude of 1142 m. The multiparameter AIRSAR data are investigated for their information content on the forest state, regarding the following questions: (1) information on forest stand parameters like forest types, age classes and crown density, especially for the separation of deciduous and coniferous forest; (2) information on the storm damages (since 1972) and the status of regeneration; (3) information on the status of forest destruction because of forest decline; and (4) influence of topography, local incidence angle and soil moisture on the SAR data. Within the project various methods and tools have been developed for the investigation of multipolarimetric radar backscatter responses and for discrimination purposes, in order to use the multipolarization information of the compressed Stokes matrix delivered by JPL

Vascular uptake of rehydration fluids in hypohydrated men at rest and exercise

The purpose of this study was to formulate and to evaluate rehydration drinks, which would restore total body water and plasma volume (PV), for astronauts to consume before and during extravehicular activity, a few hours before reentry, and immediately after landing. In the first experiment (rest, sitting), five healthy men (23-41 yr), previously dehydrated for 24 hr., drank six (1a, 2, 4, 5, 6, 7) fluid formulations (one each at weekly intervals) and then sat for 70 min. Pre-test PV were measured with Evans blue dye and changes in PV were calculated with the hematocrit-hemoglobin transformation equation. This rest experiment simulated hypohydrated astronauts preparing for reentry. The second experiment (exercise, supine) followed the same protocol except four healthy men (30-46 yr) worked for 70 min. in the supine position on a cycle ergometer at a mean load of 71+/-1 percent of their peak aerobic work capacity. This exercise experiment simulated conditions for astronauts with reduced total body water engaging in extravehicular activity

Stochastic Gravitational Wave Background from Cosmological Supernovae

Based on new developments in the understanding of supernovae (SNe) as gravitational-wave (GW) sources we estimate the GW background from all cosmic SNe. For a broad range of frequencies around 1 Hz, this background is crudely comparable to the GW background expected from standard inflationary models. While our estimate remains uncertain within several orders of magnitude, the SN GW background may become detectable by second-generation space-based interferometers such as the proposed Big-Bang Observatory (BBO). By the same token, the SN GWs may become a foreground for searches of the inflationary GWs, in particular for sub-Hz frequencies where the SN background is Gaussian and where the BBO will be most sensitive. SN simulations lasting far beyond the usual cutoff of about 1 second are needed for more robust predictions in the sub-Hz frequency band. An even larger GW background can arise from a hypothetical early population of massive stars, although their GW source strength as well as their abundance are currently poorly understood.Comment: 9 revtex pages, 8 ps figures included, considerably extended version with detailed discussion of uncertainties due to supernova physics and rate