71 research outputs found
Breaking conjugate pairing in thermostatted billiards by magnetic field
We demonstrate that in the thermostatted three-dimensional Lorentz gas the
symmetry of the Lyapunov spectrum can be broken by adding to the system an
external magnetic field not perpendicular to the electric field. For
perpendicular field vectors, there is a Hamiltonian reformulation of the
dynamics and the conjugate pairing rule still holds. This indicates that
symmetric Lyapunov spectra has nothing to do with time reversal symmetry or
reversibility; instead, it seems to be related to the existence of a
Hamiltonian connection.Comment: 4 pages, 3 figure
Master equation approach to the conjugate pairing rule of Lyapunov spectra for many-particle thermostatted systems
The master equation approach to Lyapunov spectra for many-particle systems is
applied to non-equilibrium thermostatted systems to discuss the conjugate
pairing rule. We consider iso-kinetic thermostatted systems with a shear flow
sustained by an external restriction, in which particle interactions are
expressed as a Gaussian white randomness. Positive Lyapunov exponents are
calculated by using the Fokker-Planck equation to describe the tangent vector
dynamics. We introduce another Fokker-Planck equation to describe the
time-reversed tangent vector dynamics, which allows us to calculate the
negative Lyapunov exponents. Using the Lyapunov exponents provided by these two
Fokker-Planck equations we show the conjugate pairing rule is satisfied for
thermostatted systems with a shear flow in the thermodynamic limit. We also
give an explicit form to connect the Lyapunov exponents with the
time-correlation of the interaction matrix in a thermostatted system with a
color field.Comment: 10 page
Wave Properties of Plasma Surrounding the Event Horizon of a Non-Rotating Black Hole
We have studied the wave properties of the cold and isothermal plasma in the
vicinity of the Schwarzschild black hole event horizon. The Fourier analyzed
perturbed 3+1 GRMHD equations are taken on the basis of which the complex
dispersion relations are obtained for non-rotating, rotating non-magnetized and
rotating magnetized backgrounds. The propagation and attenuation vectors along
with the refractive index are obtained (shown in graphs) to study the
dispersive properties of the medium near the event horizon. The results show
that no information can be obtained from the Schwarzschild magnetosphere.
Further, the pressure ceases the existence of normal dispersion of waves.Comment: 31 pages, 21 figures, accepted for publication in Canadian J. Phy
Auswirkungen der Landwirtschaft auf physikalische und chemische Funktionen Europäischer Torfböden
Torfböden bieten zahlreiche Funktionen: sie bilden den weltweit größten terrestrischen Kohlenstoffspeicher, stellen wichtige Nährstofffilter dar und erhöhen hydrologische Pufferkapazitäten. Torfböden sind in Mittel- und Nordeuropa zum überwiegenden Teil landwirtschaftlich genutzt. Kultivierung führt zu extremen Mineralisierungsraten der organischen Substanz und hohen THG-Emissionen. Die Anfälligigkeit für Bodensackung, Boden- und Wasserqualitätsverschlechterung und folglich Ernteausfall steigt. Das Ziel dieser Studie ist es, Auswirkungen des Agrarmanagements auf Funktionen von Torfböden in Europa zu analysieren. In Deutschland, den Niederlanden, Dänemark, Estland, Finnland und Schweden wurden standardisierte Bodenkartierungen, bodenphysikalische und -chemische Analysen, Grundwassermonitoring und Betriebsdatenerhebungen durchgeführt. Die Ergebnisse belegen einen starken Einfluss der bisherigen Bewirtschaftung auf die Funktionen von Torfböden in Europa. Torfböden unter intensiver Ackernutzung bieten im Vergleich zu extensiver und intensiver Grünlandnutzung die niedrigste Tragfähigkeit in den oberen 10 cm, welche eine erfolgreiche landwirtschaftliche Praxis auf Torfböden stark einschränkt. Der Unterschied lässt sich allein durch Wurzelstabilisierung erklären, da die Bodenverdichtung in den oberen 25cm unter Ackernutzung am höchsten ist. Hieraus folgt eine starke Verringerung der nutzbaren Feldkapazität und der gesättigten hydraulischen Leitfähigkeit, wodurch sich hydrologische Probleme wie Staunässe und Trockenstress, die häufig auf kultivierten Torfböden vorkommen, weiter intensivieren. Bodenkohlenstoffvorräte sinken deutlich mit steigender Nutzungsintensität und sind im Vergleich auf extensivem Grünland am höchsten. Dies wird bestätigt durch den Zersetzungsgrad, der hier am niedrigsten ist. Die Ergebnisse deuten auf eine starke Auswirkung des Managements auf Bodenkohlenstoffverluste und Torfkonservierung auf europäischer Ebene hin
Accelerating cycle expansions by dynamical conjugacy
Periodic orbit theory provides two important functions---the dynamical zeta
function and the spectral determinant for the calculation of dynamical averages
in a nonlinear system. Their cycle expansions converge rapidly when the system
is uniformly hyperbolic but greatly slowed down in the presence of
non-hyperbolicity. We find that the slow convergence can be associated with
singularities in the natural measure. A properly designed coordinate
transformation may remove these singularities and results in a dynamically
conjugate system where fast convergence is restored. The technique is
successfully demonstrated on several examples of one-dimensional maps and some
remaining challenges are discussed
NUNDO: a numerical model of a human torso phantom and its application to effective dose equivalent calculations for astronauts at the ISS
Control of development, secondary metabolism and light-dependent carotenoid biosynthesis by the velvet complex of Neurospora crassa
Neurospora crassa is an established reference organism to investigate carotene biosynthesis and light regulation. However, there
is little evidence of its capacity to produce secondary metabolites. Here, we report the role of the fungal-specific regulatory velvet complexes in
development and secondary metabolism (SM) in N. crassa. Three velvet proteins VE-1, VE-2, VOS-1, and a putative methyltransferase LAE-1
show light-independent nucleocytoplasmic localization. Two distinct velvet complexes, a heterotrimeric VE-1/VE-2/LAE-1 and a heterodimeric
VE-2/VOS-1 are found in vivo. The heterotrimer-complex, which positively regulates sexual development and represses asexual sporulation,
suppresses siderophore coprogen production under iron starvation conditions. The VE-1/VE-2 heterodimer controls carotene production. VE-1
regulates the expression of .15% of the whole genome, comprising mainly regulatory and developmental features. We also studied
intergenera functions of the velvet complex through complementation of Aspergillus nidulans veA, velB, laeA, vosA mutants with their
N. crassa orthologs ve-1, ve-2, lae-1, and vos-1, respectively. Expression of VE-1 and VE-2 in A. nidulans successfully substitutes the developmental and SM functions of VeA and VelB by forming two functional chimeric velvet complexes in vivo, VelB/VE-1/LaeA and VE-2/VeA/LaeA,
respectively. Reciprocally, expression of veA restores the phenotypes of the N. crassa ve-1 mutant. All N. crassa velvet proteins heterologously
expressed in A. nidulans are localized to the nuclear fraction independent of light. These data highlight the conservation of the complex
formation in N. crassa and A. nidulans. However, they also underline the intergenera similarities and differences of velvet roles according to
different life styles, niches and ontogenetic processes
Random and channeled energy loss in thin germanium and silicon crystals for positive and negative 2-15-GeV/ c
Biological Earth observation with animal sensors.
Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmen-tal change
Restoration of female fertility in Trichoderma reesei QM6a provides the basis for inbreeding in this industrial cellulase producing fungus
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