Wärme- und strömungstechnische Untersuchungen an fluchtendenRohrbündel-Wärmeaustauschern aus pyramidenförmig aufgerauhten Rohren

Integral values of heat transfer and pressure drop are reported. They have been gained from 5 tube banks in cross flow of different tube pitches and roughnesses. The experiments were conducted at Reynolds numbers 5 $\cdot$ 10$^{3}$ < Re < 10$^{6}$ with air and helium as experimental fluid on the outside of the tubes. Increasing artificially the roughness of the tubes a gain in heat transfer was achieved up to 50% compared to a tube arrangement of technically smooth tubes without increasing the flow resistance. Besides this the fraction of each tube row of the integral heat transfer coefficient of the bundle was measured. In comparison to an arrangement of smooth tubes the heat transfer of the first tube row was increased in relation to the following ones. Furthermore the artificial roughness of the tubes effected an equalisation of the velocity profiles behind the heat exchanger

An orientation experiment using auditory artificial horizon

Presented at the 10th International Conference on Auditory Display (ICAD2004)An orientation experiment was carried out in a spatially immersive virtual environment. The task of subjects was to navigate with 6 degrees of freedom flying method through a predefined route guided by visual cues. Simultaneously they should keep the model oriented in upright position as well as possible. In the experiment we had three different implementations of auditory artificial horizon, and for the reference the subjects accomplish the task also without the auditory support. According to the results the auditory artificial horizon helps subjects to keep the model oriented during the task

Improved PET Imaging of Tumors in Mice Using a Novel 18 F-Folate Conjugate with an Albumin-Binding Entity

Purpose: The folate receptor (FR) is a promising target for nuclear imaging due to its overexpression in many different cancer types. A drawback of using folate radioconjugates is the high accumulation of radioactivity in the kidneys. Therefore, the aim of this study was to develop a 18 F-labeled folate conjugate with an albumin-binding entity to enhance the blood circulation time and hence improve the tumor-to-kidney ratio. Procedures: The novel 18 F-folate was prepared by conjugation of a 18 F-labeled glucose azide to an alkyne-functionalized folate precursor containing an albumin-binding entity via Cu(I)-catalyzed 1,3-dipolar cycloaddition. The radioconjugate was tested in vitro on FR-positive KB tumor cells and by biodistribution and positron emission tomography (PET) imaging studies using KB tumor-bearing mice. Results: The radiosynthesis of the albumin-binding [18 F]fluorodeoxyglucose-folate ([18 F]3) resulted in a radiochemical yield of 1-2% decay corrected (d.c.) and a radiochemical purity of ≥95%. The specific activity of [18 F]3 ranged from 20 to 50GBq/μmol. In vitro experiments revealed FR-specific binding of [18 F]3 to KB tumor cells. In vivo we found an increasing uptake of [18 F]3 into tumor xenografts over time reaching a value of ∼ 15% injected dose (ID)/g at 4h post-injection (p.i.). Uptake in the kidneys (∼ 13% ID/g; 1h p.i.) was approximately fourfold reduced compared to previously published 18 F-labeled folic acid derivatives. An excellent visualization of tumor xenografts with an unprecedentedly high tumor-to-kidney ratio (∼ 1) was obtained by PET imaging. Conclusions: [18 F]3 showed a favorable accumulation in tumor xenografts compared to the same folate conjugate without albumin-binding properties. Moreover, the increased tumor-to-kidney ratios improved the PET imaging quality significantly, in spite of a somewhat higher background radioactivity which was a consequence of the slower blood clearance of [18 F]

An improved folate stable isotope dilution assay of unexploited food sources from Brazil

Brazil has a diverse plant community, including underutilized non-conventional food crops (PANCs), which have the potential to be a rich source of food and contribute to food security. For assessing the folate content in a range of Brazilian PANCs, we extended the validation of an existing stable isotope dilution assay (SIDA) for the stably 13C-labelled 10-formyl-Pte[13C5]Glu (10-CHO-Pte[13C5]Glu). The SIDA method with an enzymatic treatment, purification step, and an LC–MS/MS measurement was validated regarding linearity, precision, LoD/LoQ, and recovery for 10-CHO-PteGlu. After successful validation, the study of some underutilized Brazilian non-conventional fruits and leaves from the São Paulo State University campus revealed them as an important source of folates. It provided the first insights into the folate content of unexploited food sources from Brazil. Pequi had the highest folate content among the fruits studied, with mean values of 333 μg/100 g based on fresh weight (FW). The analysis also shows that different cultivars of fruit or fruits from different growing locations have a high variability in folate content or other nutritional factors. In most fruits, the main vitamer was 5-CH3-H4folate, but jenipapo and taioba showed the highest content of 10-CHO-PteGlu with 28.22 μg/100 g (FW) in jenipapo peel and 75.64 μg/100 g (FW) in the taioba leaves. Thus, this study also provides results on the importance of the folate vitamer 10-CHO-PteGlu contributing to the total folate content

Localization of a moving virtual sound source in a virtual room, the effect of a distracting auditory stimulus

Presented at the 8th International Conference on Auditory Display (ICAD), Kyoto, Japan, July 2-5, 2002.An audio localization test of moving virtual sound sources was carried out in a spatially immersive virtual environment, using loudspeaker array with vector based amplitude panning for reproduction of sound sources. Azimuth and elevation error in localization was measured. In this experiment the main emphasis was to explore the effect of a distracting auditory stimulus. Eight subjects accomplished a set of localization tasks. In these tasks they perceived the azimuth more accurately than the elevation. The distracting auditory stimulus decreased the localization accuracy. There was large variation between the subjects. The median error in azimuth for the most inaccurate subject was approximately twice as much as for the most accurate subject. The amount of the localization blur was dependent on angular distance from virtual sound source position to the nearest loudspeaker. The localization blur increased while the angular distance increased. Results of this experiment were compared with the results achieved in our previous experiment without the distracting stimulus

Digitale Simulation regenerativer elektrischer Energieversorgungssysteme

Available from TIB Hannover: DW 3765 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman