2,209 research outputs found
Endoscopically Based Endonasal and Transnasal Lasersurgery
The endoscopically based endonasal and transnasal laser surgery is
a surgical procedure, which offers the ENT-specialist a safe and
effective method to cure or to improve a number of diseases of the
upper and middle airways. Coagulative lasers are used in contact
and noncontact mode. Their light is mainly absorbed by hemoglobin
but rarely by water. The laser–tissue interaction is performed via
flexible glass fibers. For the delivery of the laser beam we use
specially designed applicator sheaths, which incorporate the
endoscope, the laser fiber and the suction channel. The procedure
is controlled online via the endoscopic image on the monitor
(“video-endoscopy”). The patient suffers less trauma
using this treatment compared to the standard endoscopic surgery
and the procedure is much quicker. Pre- and post-operative
rhinomanometric and rhinoresistometric measurements reveal that
the air flow rate of the nose can be improved effectively
Switching dynamics of spatial solitary wave pixels
Separatrices and scaling laws in the switching dynamics of spatial solitary wave pixels are investigated. We show that the dynamics in the full model are similar to those in the plane-wave limit. Switching features may be indicated and explained by the motion of the (complex) solitary wave amplitude in the phase plane. We report generalization, into the domain of transverse effects, of the pulse area theorem for the switching process and a logarithmic law for the transient dynamics. We also consider, for what is the first time to our knowledge, phase-encoded address of solitary pixels and find that a near-square-wave temporal switching pattern is permitted without (transverse) cross switching
[2.2](4,7)Isobenzofuranophanes - Synthesis, Characterisation and Reactivity
The isomeric Diels-Alder adducts 3, obtained by cycloaddition of tetraphenylcyclopentadienone to the 4,5:12,13-bis-(oxanorbornadieno)[2.2]paracyclophanes syn,syn- and anti,-syn-2[Note ][The stereochemical descriptors syn and anti refer to the orientation of the oxygen bridge in the oxabicyclo[2.2.1]heptadiene subunits with respect to the [2.2]paracyclophaneskeleton.], yield the unstable isobenzofuranophane 4 by consecutive extrusion of carbon monoxide and tetraphenylbenzene when heated to 180°C. The molecular ion of 4 was observed in the EI mass spectrum. The stable tetraphenyl-substituted analogue 10 was synthesized independently from the previously unknown 4,5,12,13-tetrabenzoyl[2.2]paracyclophane (9). UV/Vis as well as fluorescence spectra and an X-ray crystal structure analysis of 9 are reported
Re-entrant Nematic Phase Established for Several Homologous Biaromatic Liquid Crystals by Investigation of Binary Mixed Systems
Several homologous series of biaromatic liquid crystals with structure type CnH2n+1O • C6H4 • M•C6H4-CN are investigated. By studying the phase transition temperatures in binary mixed systems a "re-entrant" nematic phase N(re) is established for all compounds exhibiting smectic A phases. The virtual transition temperatures N(re) - SA are found to decrease with increasing chain length of the alkyloxy group. The influence of the middle group M on the re-entrant behaviour can be attributed mainly to its dipole moment. The temperature range of the smectic A phase decreases when the middle group dipole moment is additive to that of the nitrile group. To summarize it can be said that the "re-entrant" behaviour of biaromatic liquid crystals is found to be very similar to that of triaromatic systems reported recently
Cohomogeneity one manifolds and selfmaps of nontrivial degree
We construct natural selfmaps of compact cohomgeneity one manifolds with
finite Weyl group and compute their degrees and Lefschetz numbers. On manifolds
with simple cohomology rings this yields in certain cases relations between the
order of the Weyl group and the Euler characteristic of a principal orbit. We
apply our construction to the compact Lie group SU(3) where we extend identity
and transposition to an infinite family of selfmaps of every odd degree. The
compositions of these selfmaps with the power maps realize all possible degrees
of selfmaps of SU(3).Comment: v2, v3: minor improvement
Substantia nigra activity level predicts trial-to-trial adjustments in cognitive control
Effective adaptation to the demands of a changing environment requires flexible cognitive control. The medial and the lateral frontal cortices are involved in such control processes, putatively in close interplay with the BG. In particular, dopaminergic projections from the midbrain (i.e., from the substantia nigra [SN] and the ventral tegmental area) have been proposed to play a pivotal role in modulating the activity in these areas for cognitive control purposes. In that dopaminergic involvement has been strongly implicated in reinforcement learning, these ideas suggest functional links between reinforcement learning, where the outcome of actions shapes behavior over time, and cognitive control in a more general context, where no direct reward is involved. Here, we provide evidence from functional MRI in humans that activity in the SN predicts systematic subsequent trial-to-trial RT prolongations that are thought to reflect cognitive control in a stop-signal paradigm. In particular, variations in the activity level of the SN in one trial predicted the degree of RT prolongation on the subsequent trial, consistent with a modulating output signal from the SN being involved in enhancing cognitive control. This link between SN activity and subsequent behavioral adjustments lends support to theoretical accounts that propose dopaminergic control signals that shape behavior both in the presence and in the absence of direct reward. This SN-based modulatory mechanism is presumably mediated via a wider network that determines response speed in this task, including frontal and parietal control regions, along with the BG and the associated subthalamic nucleus
The Gap-Tooth Method in Particle Simulations
We explore the gap-tooth method for multiscale modeling of systems
represented by microscopic physics-based simulators, when coarse-grained
evolution equations are not available in closed form. A biased random walk
particle simulation, motivated by the viscous Burgers equation, serves as an
example. We construct macro-to-micro (lifting) and micro-to-macro (restriction)
operators, and drive the coarse time-evolution by particle simulations in
appropriately coupled microdomains (teeth) separated by large spatial gaps. A
macroscopically interpolative mechanism for communication between the teeth at
the particle level is introduced. The results demonstrate the feasibility of a
closure-on-demand approach to solving hydrodynamics problems
Investigations on Large Turbine Bearings Working Under Transitional Conditions Between Laminar and Turbulent Flow
Weak in Space, Log in Time Improvement of the Lady{\v{z}}enskaja-Prodi-Serrin Criteria
In this article we present a Lady{\v{z}}enskaja-Prodi-Serrin Criteria for
regularity of solutions for the Navier-Stokes equation in three dimensions
which incorporates weak norms in the space variables and log improvement
in the time variable.Comment: 14 pages, to appea
Quasi-Gaussian Statistics of Hydrodynamic Turbulence in 3/4+\epsilon dimensions
The statistics of 2-dimensional turbulence exhibit a riddle: the scaling
exponents in the regime of inverse energy cascade agree with the K41 theory of
turbulence far from equilibrium, but the probability distribution functions are
close to Gaussian like in equilibrium. The skewness \C S \equiv
S_3(R)/S^{3/2}_2(R) was measured as \C S_{\text{exp}}\approx 0.03. This
contradiction is lifted by understanding that 2-dimensional turbulence is not
far from a situation with equi-partition of enstrophy, which exist as true
thermodynamic equilibrium with K41 exponents in space dimension of . We
evaluate theoretically the skewness \C S(d) in dimensions ,
show that \C S(d)=0 at , and that it remains as small as \C
S_{\text{exp}} in 2-dimensions.Comment: PRL, submitted, REVTeX 4, 4 page
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