25 research outputs found
single nucleotide polymorphism profiles of patients with acute renal rejection to personalize immunosuppressive therapy preliminary results from an on going italian study
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Mitochondrial physiology
As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery
Mitochondrial physiology
As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery
Realizzazione di un'applicazione web per la gestione dei cespiti in un contesto multinazionale
Erstellung eines Konzepts fĂŒr E-Learning-Angebote zur Vermittlung von Informationskompetenz an der Bibliothek der Hochschule fĂŒr angewandte Wissenschaft und Kunst HAWK Hildesheim/Holzminden/Göttingen am Beispiel von zwei Kurseinheiten
Zustimmung des Autors zur Veröffentlichung des Abstracts nicht erteilt
Numerical modelling of swept and crossing shock-wave turbulent boundary-layer interactions
Two configurations that have received a great deal of attention in the last decades are namely the
single-fin and double-fin. In these interactions, deflected un-swept sharp fins are used to generate
single-swept and double-crossing oblique shock-waves that interact with a supersonic/hypersonic
turbulent boundary-layer developing over a flat plate. Following the swept-shock interaction, the
study of crossing-shock interaction represents a logical progression in the general study of shock-
wave / turbulent boundary-layer interactions (SWTBLIS). These rather simple geometries allow
isolating the inherent flow physics which can be applied to more complex configurations.
Besides having fundamental importance, swept- and crossing-shock interactions also have
important engineering applications. Research findings on single-fin can be applied, for example, in
the design of wing/tail fuselage juncture, and in high incidence flows on swept delta wings and
slender bodies. The double-fin, on the other hand, could represent a simplification of a high-speed
inlet of vehicles employing air-breathing propulsion. Such an inlet geometry concepts employ side-
wall compression to increase, in reasonable short distance, the air pressure prior combustion. The
side-wall compression surfaces (i.e. fins) generate an oblique shock-wave that crosses one another
and interacts with the boundary-layer developing on the windward of the fiJselage. The nature of
such complex 3-D interactions can affect the performance of the inlet as well as the engine. If the
physical principles governing these interactions are well determined and understood, then an active
control system can be developed so that to reduce the risk of engine fail and optimise its
performance. Note that the findings of this investigation are crucial for the design of effective
thermal protection systems since these interactions produce high peaks of heating which can
damage materials severely around concentrated areas where shock-waves hit surfaces.
The main objective of this thesis is to predict accurately secondary separation flows and wall heat
transfer under conditions of turbulent and separated flow, which has represented a challenging
problem for computational fluid dynamists for the past thirty years.
Steady RANS modelling has been carried out for a symmetrical double-sharp-fin configuration
with an inclination angles from 7 degrees to 21 degrees, Mach 3.92 and Reynolds number RC5 = 3.08X105, aiming
for comparison and improvement of wall heat transfer predictions. Grid refinement and turbulence
modelling studies have been carried out carefully in order to improve previous numerical predictions against experimental measurements. Overall, current steady Reynolds Averaged
Navier-Stokes computations with co-based Reynolds Stress Model (RANS-RSM) outperformed
one- and two-equation conventional turbulence models as well as other numerical investigations
carried out over the last three decades.
My original contribution to knowledge focuses primarily on improving numerical prediction of
wall heat transfer in supersonic/hypersonic side-wall compression inlets and deflected aerodynamic
surfaces. Different methods of evaluation of the wall heat transfer, to improve the comparison with
available experiments, have been proposed for both single- and double-fin configurations. Results
are compared with experimental measurements and previous numerical studies. The most
challenging numerical prediction of wall heat transfer coefficient in strong pressure gradient flows
has been largely improved, for the first time, by adopting three approaches: (1) choosing a suitable
turbulence model - the wall heat transfer coefficients peaks computed by RANS-RSM are in fact
closer to experimental peaks (50% improvement) in comparison with other conventional two-
equation eddy-viscosity turbulence models; (2) increasing the wall turbulent Prandtl number in
region of high shear strain; (3) and finally, adopting a pressure-based correlation formula. The
latter appeared to be the most effective method of predicting wall heat transfer coefficient,
provided accurate wall pressure distributions being obtained by numerical simulations.
Within the scope of this original research, complex flow structures are also numerically
investigated in detail to verify and further examine, existing conclusions on the nature of incipient
and secondary separation evolution at monotonic increasing shock strengths, for the single-fin
configurations at Mach numbers 3, 4 and 5 and at beta finâs deflection angles [if ranging from 9 degrees to
30.6 degrees. The nature of secondary separation will be explained at different regimes III-VI in condition
of subsonic and supersonic transverse conical cross-flow.
Computational Fluid Dynamics (CFD) analyses using conventional two-equation turbulence
models are unable to capture secondary flow separations at moderate interaction strength - a
phenomenon observed in experiments and believed to be associated with a âweakly-turbulentâ
boundary-layer separation. I investigated this aspect in further details. In fact, RANS-RSM, due to
its capability of reproducing correct level of turbulence kinetic energy (TKE), confirmed the
presence of such a âweakly-turbulentâ state of transverse cross-flow in the near-wall regions
underneath the main cross-flow vortex at moderate interaction strength (regime 111/] V).
Computations revealed that the development of the secondary separation at early stage (regime III)
is caused by the interaction of (1) the âconically-subsonicâ (Mn < 1) flow region of the transverse cross-flow developed from the primary reattachment (R[sub 1]) line with (2) the subsonic (M < 1) region
of the near-wall secondary cross-flow which forms within the primary separation zone.
Turbulence behaviour was also analysed, for the first time, in the reverse cross-flow in order to
investigate the influence of the (laminar or turbulent) flow state in evolution of secondary
separation phenomenon at increasing shock strengths. Remarkably, computed results are in good
agreement with the conclusions of experimentalists. In fact, the secondary separation (S[sub 2]) cross-
flow gradually disappears in transitional (laminar-to-turbulent) supersonic conical cross-flow
regions (regimes IV and V), except at the regime VI, where S[sub 2] reappears, accompanied by a
secondary reattachment (R[sub 2]) line, once the supersonic conical cross-flow becomes fully-developed
turbulent. At this stage, the embedded normal shock-wave reaches the critical shock strength (xi[sub i]-
1.56) which is typically required to force turbulent separation. This study demonstrated
numerically that the critical value xi[sub i]= 1.5 corresponds to the incipient secondary separation
condition which is typical for the separated turbulent flows (regime V). A careful quantitative and
qualitative analysis on the developments of the turbulence kinetic energy across the 3-D domain
excitingly also confirms these findings. Thus, it was concluded that evolution of the secondary
separation phenomenon at increasing shock strengths is influenced not only by the acceleration of
the transverse cross-flow to conically-supersonic regime but also by some physical mechanisms
that amplify the turbulence levels in the near-wall reverse cross-flow.
One unique feature of the crossing-shock interaction at regime III; i.e. the secondary separation
phenomenon, initially observed in the single-fin flow, has been successfully reproduced in a
double-fin configuration by numerical computation using RANS-RSM. CFD predicted 3-D flow
stream-surfaces showed that the initially weak secondary separation has been further strengthened
in span-wise direction towards the central separated zone. Additional flow topology at stronger
crossing-shock interactions has been also presented showing the evolution of surface flow-pattems
at increasing shock strengths.
To the authorâs knowledge, the present study represents the first attempt to predict the evolution of
secondary separation phenomenon in single- and double-fin configurations at different interaction
regimes. Findings suggest that the classification originally made by Zheltovodov er al. for single-
fin flows (hence for Swept-Shock-Wave/Turbulent Boundary-Layer Interaction, S-SWTBLI) can
be also applied to double-fin configurations (thus for Crossing-Shock-Wave/Turbulent Boundary-
Layer Interaction, C-SWTBLI)
Flow topology and secondary separation modelling at crossing shock wave/turbulent boundary layer interaction conditions
Steady RANS modelling has been carried out for a symmetrical double-sharp-fin configuration with an inclination angle 15°, Mach 3.92 and Reynolds number ReÎŽ = 3.08 x 105. Grid refinement and turbulence model influences using Ï-based Reynolds Stress model (RSM), one-equation Eddy Viscosity Transport and two-equation Shear Stress Transport, have been studied and predicted wall pressure distributions were in good agreement with experiment data. RSM model surface flow topology was found to be in better qualitatively agreement with experimental oil-flow visualization than those from other two models. The secondary separation phenomenon observed in the experiment was successfully reproduced by the RSM model, due to its ability to evaluate correct level of turbulence kinetic energy that is critical in determining pseudo-laminar state of an embedded reversed flow underneath the main cross-flow vortex. Three-dimensional flow structures demonstrated that the initially weak secondary separation has been further strengthened in span-wise direction towards the central separated zone