Regeneratives Heizen und Kuehlen mit halbem Brennstoffverbrauch Abschlussbericht

It was demonstrated in the context of the joint research project that the Vuilleumier cycle offers the best chances of implementation as a heat pump in a domestic heating system. Efficiencies of over 150% were measured. A compact radiant burner with an integrated air preheater was developed for heating the heat pump. The results show that the burner concept fully satisfies the requirements in terms of emissions. The values measured show that both the NO_x and CO emissions in the exhaust gas are below 10 ppm. With regard to the efficiency of the burner, which ranges between 75 and 80% at the combustion air temperatures attained of approx. 450 C, the interim position reached does not fully satisfy the requirements. In order to achieve the burner efficiency of 90% as defined by the product requirement specifications, the combustion air temperature must be increased to at least 500 C. This is the subject of further development work. (orig.)Im Rahmen des Verbundvorhabens konnte nachgewiesen werden, dass der Vuilleumier-Kreizprozess die besten Chancen fuer die Umsetzung als Waermepumpe in einem Hausheizungssystem bietet. Es wurden Nutzungsgrade von ueber 150% nachgewiesen. Zur Beheizung der Waermepumpe wurde ein kompakter Strahlungsbrenner mit integriertem Luftvorwaermer entwickelt. Die Ergebnisse zeigen, dass das Brennerkonzept im Hinblick auf die Schadgasemissionen, die Anforderungen im vollen Umfang erfuellt. Die ermittelten Messwerte zeigen, dass sowohl die NO_x- als auch die CO-Emissionen im Abgas unterhalb von 10 ppm liegen. Im Hinblick auf den Brennerwirkungsgrad, der bei den erreichten Verbrennungsluft-Temperaturen von ca. 450 C zwischen 75 und 80% liegt, wurde ein Zwischenstand erreicht, der die Anforderungen noch nicht im vollen Umfang erfuellt. Um den im Anforderungskatalog festgelegten Brennerwirkungsgrad von 90% zu erhalten, muss die Verbrennungsluft-Temperatur auf mindestens 500 C erhoeht werden. Dies ist Gegenstand weiterer Entwicklungsarbeiten. (orig.)SIGLEAvailable from TIB Hannover: F97B1317+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Dependence of resting-state fMRI fluctuation amplitudes on cerebral cortical orientation relative to the direction of B0 and anatomical axes

Functional magnetic resonance imaging (fMRI) is now capable of sub-millimetre scale measurements over the entire human brain, however with such high resolutions each voxel is influenced by the local fine-scale details of the cerebral cortical vascular anatomy. The cortical vasculature is structured with the pial vessels lying tangentially along the grey matter surface, intracortical diving arterioles and ascending venules running perpendicularly to the surface, and a randomly oriented capillary network within the parenchyma. It is well-known that the amplitude of the blood-oxygenation level dependent (BOLD) signal emanating from a vessel depends on its orientation relative to the field. Thus the vascular geometric hierarchy will impart an orientation dependence to the BOLD signal amplitudes and amplitude differences due to orientation differences constitute a bias for interpreting neuronal activity. Here, we demonstrate a clear effect of cortical orientation to in the resting-state BOLD-fMRI amplitude (quantified as the coefficient of temporal signal variation) for 1.1 mm, isotropic data at 7T and 2 mm, isotropic at 3T. The maximum bias, i.e. the fluctuation amplitude difference between regions where cortex is perpendicular to vs. parallel to , is about at the pial surface at 7T and at 3T. The orientation bias declines with cortical depth, becomes progressively smaller closer to the white matter surface, but then increases again to a local maximum within the white matter just beneath the cortical grey matter, suggesting a distinct tangential network of white matter vessels that also generate a BOLD orientation effect. We further found significant (negative) biases with the cortex orientation to the anterior-posterior anatomical axis of the head: a maximum negative bias of about at the pial surface at 7T and about at 3T. The amount of signal variance explained by the low frequency drift, motion and the respiratory cycle also showed a cortical orientation dependence; only the cardiac cycle induced signal variance was independent of cortical orientation, suggesting that the cardiac induced component of the image time-series fluctuations is not related to a significant change in susceptibility. Although these orientation effects represent a signal bias, and are likely to be a nuisance in high-resolution analyses, they may help characterize the vascular influences on candidate fMRI acquisitions and, thereby, may be exploited to improve the neuronal specificity of fMRI

The EPI rs-fMRI signal shows an orientation effect with respect to B0 and phase-encode axis across cortical depth

The cortex exhibits a strict vascular architecture and vessel orientation to the B0 field should impact the local susceptibility and hence the local BOLD signal. Cortical folding could thus lead to local variations in the signal. Here, we used high-resolution 7T EPI rs-fMRI data and found substantial variations of the signal amplitdude's coefficient of variation (σ/μ) with the local cortical orientation to B0. This effect was measurable throughout cortical depths with a maximised effect of +70 at the surface. We compare this to orientation-dependent blurring effects along the phase-encode axis, which we found to be significant too

Monica-Projekt, Region Augsburg: Handbuch Ueberblick 1984/85

TIB Hannover: RO 2674+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman