67 research outputs found
(Ent-)Hemmung bei Lacan
Lacan, oft verschrien als bis ins Absurde hinein intellekÂtualisierend, kann nachgerade als Theoretiker des Affekts aufgefasst werden. Seine unorthodoxe WeiterfĂĽhrung von Freuds Dreifaltigkeit «Hemmung–SympÂtom– Angst» entwickelt zunächst ein um sechs weitere Haltungen erweiterÂtes Diagnoseschema, das Patienten anhand typischer Angstvermeidungsmuster einschätzt. Hemmung bedeutet dabei motorischer, aber auch emotionaler StillÂstand und hat am wenigsten Witz. Lacan korrigiert, dass die zu Freuds Zeitalter Gehemmten heute eher die «Verhinderten» seien, die «begehren, nicht zu können». Später behauptet er, dass Hemmung auftrete, wenn Bildhaftes zu sehr den Ablauf von Assoziationsketten störe. Heute ist Lacan vor allem mit der Bestimmung des Zeitgeistes als auferlegtem (und damit gehemmtem) Genuss aktuell. Immer wieÂder wird er von Kulturphilosophen als Stichwortgeber aufgerufen, wo sie nachÂvollziehen möchten, warum das Zeitalter des Gottestodes bzw. der Befreiung von Tabus paradoxerweise mit noch mehr ĂśberÂIchÂStrenge einhergeht. Lacan ist eher skeptisch, was Möglichkeiten einer wahrhaft befreienden Enthemmung angeht
On the spin--boson model with a sub--Ohmic bath
We study the spin--boson model with a sub--Ohmic bath using infinitesimal
unitary transformations. Contrary to some results reported in the literature we
find a zero temperature transition from an untrapped state for small coupling
to a trapped state for strong coupling. We obtain an explicit expression for
the renormalized level spacing as a function of the bare papameters of the
system. Furthermore we show that typical dynamical equilibrium correlation
functions exhibit an algebaric decay at zero temperature.Comment: 9 pages, 2 Postscript figure
Cluster-based reduced-order modelling of a mixing layer
We propose a novel cluster-based reduced-order modelling (CROM) strategy of
unsteady flows. CROM combines the cluster analysis pioneered in Gunzburger's
group (Burkardt et al. 2006) and and transition matrix models introduced in
fluid dynamics in Eckhardt's group (Schneider et al. 2007). CROM constitutes a
potential alternative to POD models and generalises the Ulam-Galerkin method
classically used in dynamical systems to determine a finite-rank approximation
of the Perron-Frobenius operator. The proposed strategy processes a
time-resolved sequence of flow snapshots in two steps. First, the snapshot data
are clustered into a small number of representative states, called centroids,
in the state space. These centroids partition the state space in complementary
non-overlapping regions (centroidal Voronoi cells). Departing from the standard
algorithm, the probabilities of the clusters are determined, and the states are
sorted by analysis of the transition matrix. Secondly, the transitions between
the states are dynamically modelled using a Markov process. Physical mechanisms
are then distilled by a refined analysis of the Markov process, e.g. using
finite-time Lyapunov exponent and entropic methods. This CROM framework is
applied to the Lorenz attractor (as illustrative example), to velocity fields
of the spatially evolving incompressible mixing layer and the three-dimensional
turbulent wake of a bluff body. For these examples, CROM is shown to identify
non-trivial quasi-attractors and transition processes in an unsupervised
manner. CROM has numerous potential applications for the systematic
identification of physical mechanisms of complex dynamics, for comparison of
flow evolution models, for the identification of precursors to desirable and
undesirable events, and for flow control applications exploiting nonlinear
actuation dynamics.Comment: 48 pages, 30 figures. Revised version with additional material.
Accepted for publication in Journal of Fluid Mechanic
Flow separation control using optical feedback
Flow separation induced by adverse pressure gradients leads in many engineering applications to severe losses and restrictions of operation range. For example, detached flow on wings leads to drag increase and lift decrease, while compressor stall can lead to thrust reduction accompanied by dangerous unsteady loads. The mitigation of flow separation remains, therefore, an ongoing challenge and a quintessential goal of flow control
Drag reduction of a blunt body by unsteady shear layer forcing and Coanda blowing
Nous étudions les effets d'un forçage périodique du sillage sur la traînée d'un corps non-profilé au culot droit. Avec la combinaison des jets pulsés et d'une surface courbée, le contrôle augmente de 30% la pression au culot grâce à l'effet Coanda et à la periodicité des jets. La fréquence d'actuation est un ordre de grandeur plus élevé que les instabilités du sillage. Avec la vélocimétrie par image de particules, nous observons que l'actuation diminue la section verticale du sillage et modifie l'evolution de la vorticité des couches cisaillées. Toutefois, la dynamique du sillage proche ne semble pas être modifiée qualitativement. We analyze the effects of periodic forcing on the wake and drag of a square back bluff body. In combination with a Coanda effect, shear-layer forcing by periodic blowing allows to recover over 30% of the base pressure. The actuation frequency is an order of magnitude higher than the natural shear-layer instabilities. Velocity measurements indicate that the forced wake is thinner and that the vorticity along the shear layer development is modified. However, the wake dynamics further downstream remains very similar to the unforced vortex shedding mode.We analyze the effects of periodic forcing on the wake and drag of a square back bluff body. In combination with a Coanda effect, shear-layer forcing by periodic blowing allows to recover over 30% of the base pressure. The actuation frequency is an order of magnitude higher than the natural shear-layer instabilities. Velocity measurements indicate that the forced wake is thinner and that the vorticity along the shear layer development is modified. However, the wake dynamics further downstream remains very similar to the unforced vortex shedding mode
Soil microbial CNP and respiration responses to organic matter and nutrient additions: evidence from a tropical soil incubation
Soil nutrient availability has a strong influence on the fate of soil carbon (C) during microbial decomposition, contributing to Earth's C balance. While nutrient availability itself can impact microbial physiology and C partitioning between biomass and respiration during soil organic matter decomposition, the availability of labile C inputs may mediate the response of microorganisms to nutrient additions. As soil organic matter is decomposed, microorganisms retain or release C, nitrogen (N) or phosphorus (P) to maintain a stoichiometric balance. Although the concept of a microbial stoichiometric homeostasis has previously been proposed, microbial biomass CNP ratios are not static, and this may have very relevant implications for microbial physiological activities. Here, we tested the hypothesis that N, P and potassium (K) nutrient additions impact C cycling in a tropical soil due to microbial stoichiometric constraints to growth and respiration, and that the availability of energy-rich labile organic matter in the soil (i.e. leaf litter) mediates the response to nutrient addition. We incubated tropical soil from French Guiana with a ¹³C labeled leaf litter addition and with mineral nutrient additions of +K, +N, +NK, +PK and +NPK for 30 days. We found that litter additions led to a ten-fold increase in microbial respiration and a doubling of microbial biomass C, along with greater microbial N and P content. We found some evidence that P additions increased soil CO² fluxes. Additionally, we found microbial biomass CP and NP ratios varied more widely than CN in response to nutrient and organic matter additions, with important implications for the role of microorganisms in C cycling. The addition of litter did not prime soil organic matter decomposition, except in combination with +NK fertilization, indicating possible P-mining of soil organic matter in this P-poor tropical soil. Together, these results point toward an ultimate labile organic substrate limitation of soil microorganisms in this tropical soil, but also indicate a complex interaction between C, N, P and K availability. This highlights the difference between microbial C cycling responses to N, P, or K additions in the tropics and explains why coupled C, N and P cycling modeling efforts cannot rely on strict microbial stoichiometric homeostasis as an underlying assumption
Clinical and molecular characterization of isolated M1 disease in pediatric medulloblastoma: experience from the German HIT-MED studies
PURPOSE: To evaluate the clinical impact of isolated spread of medulloblastoma cells into cerebrospinal fluid without additional macroscopic metastases (M1-only). METHODS: The HIT-MED database was searched for pediatric patients with M1-only medulloblastoma diagnosed from 2000 to 2019. Corresponding clinical and molecular data was evaluated. Treatment was stratified by age and changed over time for older patients. RESULTS: 70 patients with centrally reviewed M1-only disease were identified. Clinical data was available for all and molecular data for 45/70 cases. 91% were non-WNT/non-SHH medulloblastoma (Grp3/4). 5-year PFS for 52 patients ≥ 4 years was 59.4 (± 7.1) %, receiving either upfront craniospinal irradiation (CSI) or SKK-sandwich chemotherapy (CT). Outcomes did not differ between these strategies (5-year PFS: CSI 61.7 ± 9.9%, SKK-CT 56.7 ± 6.1%). For patients < 4 years (n = 18), 5-year PFS was 50.0 (± 13.2) %. M1-persistence occurred exclusively using postoperative CT and was a strong negative predictive factor (p(PFS/OS) < 0.01). Patients with additional clinical or molecular high-risk (HR) characteristics had worse outcomes (5-year PFS 42.7 ± 10.6% vs. 64.0 ± 7.0%, p = 0.03). In n = 22 patients ≥ 4 years with full molecular information and without additional HR characteristics, risk classification by molecular subtyping had an effect on 5-year PFS (HR 16.7 ± 15.2%, SR 77.8 ± 13.9%; p = 0.01). CONCLUSIONS: Our results confirm that M1-only is a high-risk condition, and further underline the importance of CSF staging. Specific risk stratification of affected patients needs attention in future discussions for trials and treatment recommendations. Future patients without contraindications may benefit from upfront CSI by sparing risks related to higher cumulative CT applied in sandwich regimen. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11060-021-03913-5
Clinical and molecular characterization of isolated M1 disease in pediatric medulloblastoma: experience from the German HIT-MED studies
PURPOSE: To evaluate the clinical impact of isolated spread of medulloblastoma cells into cerebrospinal fluid without additional macroscopic metastases (M1-only).
METHODS: The HIT-MED database was searched for pediatric patients with M1-only medulloblastoma diagnosed from 2000 to 2019. Corresponding clinical and molecular data was evaluated. Treatment was stratified by age and changed over time for older patients.
RESULTS: 70 patients with centrally reviewed M1-only disease were identified. Clinical data was available for all and molecular data for 45/70 cases. 91% were non-WNT/non-SHH medulloblastoma (Grp3/4). 5-year PFS for 52 patients ≥ 4 years was 59.4 (± 7.1) %, receiving either upfront craniospinal irradiation (CSI) or SKK-sandwich chemotherapy (CT). Outcomes did not differ between these strategies (5-year PFS: CSI 61.7 ± 9.9%, SKK-CT 56.7 ± 6.1%). For patients < 4 years (n = 18), 5-year PFS was 50.0 (± 13.2) %. M1-persistence occurred exclusively using postoperative CT and was a strong negative predictive factor (p < 0.01). Patients with additional clinical or molecular high-risk (HR) characteristics had worse outcomes (5-year PFS 42.7 ± 10.6% vs. 64.0 ± 7.0%, p = 0.03). In n = 22 patients ≥ 4 years with full molecular information and without additional HR characteristics, risk classification by molecular subtyping had an effect on 5-year PFS (HR 16.7 ± 15.2%, SR 77.8 ± 13.9%; p = 0.01).
CONCLUSIONS: Our results confirm that M1-only is a high-risk condition, and further underline the importance of CSF staging. Specific risk stratification of affected patients needs attention in future discussions for trials and treatment recommendations. Future patients without contraindications may benefit from upfront CSI by sparing risks related to higher cumulative CT applied in sandwich regimen
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