2,094 research outputs found
Some chirality-related properties of the 4-D massive Dirac propagator and determinant in an arbitrary gauge field
For a 4-D massive Dirac field in the background of arbitrary gauge fields, we
show that the Dirac propagator and functional determinant are completely
determined by knowledge of the corresponding quantities for just one of the
chirality sectors of the second-order Dirac operator. This generalizes the
related, previously known, statements in (anti-)self-dual background gauge
fields. The logarithms of the (renormalized) functional determinants from the
two chirality sectors are shown to be different only by a term reflecting the
integrated chiral anomaly.Comment: 17 pages, late
Instanton Determinant with Arbitrary Quark Mass: WKB Phase-shift Method and Derivative Expansion
The fermion determinant in an instanton background for a quark field of
arbitrary mass is studied using the Schwinger proper-time representation with
WKB scattering phase shifts for the relevant partial-wave differential
operators. Previously, results have been obtained only for the extreme small
and large quark mass limits, not for intermediate interpolating mass values. We
show that consistent renormalization and large-mass asymptotics requires up to
third-order in the WKB approximation. This procedure leads to an almost
analytic answer, requiring only modest numerical approximation, and yields
excellent agreement with the well-known extreme small and large mass limits. We
estimate that it differs from the exact answer by no more than 6% for generic
mass values. In the philosophy of the derivative expansion the same amplitude
is then studied using a Heisenberg-Euler-type effective action, and the leading
order approximation gives a surprisingly accurate answer for all masses.Comment: 15 pages, 3 figure
The voltage-gated potassium channel Shaker promotes sleep via thermosensitive GABA transmission
Genes and neural circuits coordinately regulate animal sleep. However, it remains elusive how these endogenous factors shape sleep upon environmental changes. Here, we demonstrate that Shaker (Sh)-expressing GABAergic neurons projecting onto dorsal fan-shaped body (dFSB) regulate temperature-adaptive sleep behaviors in Drosophila. Loss of Sh function suppressed sleep at low temperature whereas light and high temperature cooperatively gated Sh effects on sleep. Sh depletion in GABAergic neurons partially phenocopied Sh mutants. Furthermore, the ionotropic GABA receptor, Resistant to dieldrin (Rdl), in dFSB neurons acted downstream of Sh and antagonized its sleep-promoting effects. In fact, Rdl inhibited the intracellular cAMP signaling of constitutively active dopaminergic synapses onto dFSB at low temperature. High temperature silenced GABAergic synapses onto dFSB, thereby potentiating the wake-promoting dopamine transmission. We propose that temperature-dependent switching between these two synaptic transmission modalities may adaptively tune the neural property of dFSB neurons to temperature shifts and reorganize sleep architecture for animal fitness.
Ji-hyung Kim and Yoonhee Ki et al. show that low temperatures suppress sleep in Drosophila by increasing GABA transmission in Shaker-expressing GABAergic neurons projecting onto the dorsal fan-shaped body, while high temperatures potentiate dopamine-induced arousal by reducing GABA transmission. This study highlights a role for Shaker in sleep modulation via a temperature-dependent switch in GABA signaling
Comparing the Heterogeneity of Copper-Binding Characteristics for Two Different-Sized Soil Humic Acid Fractions Using Fluorescence Quenching Combined with 2D-COS
Heterogeneous distributions of copper-binding characteristics were compared for two ultrafiltered size fractions of a soil HA using fluorescence quenching combined with two-dimensional correlation spectroscopy (2D-COS). The apparent shapes of the original synchronous fluorescence spectra and the extent of the fluorescence quenching upon the addition of copper were similar for the two fractions. The stability constants calculated at their highest peaks were not significantly different. However, the 2D-COS results revealed that the fluorescence quenching behaviors were strongly affected by the associated wavelengths and the fraction's size. The spectral change preferentially occurred in the wavelength order of 467 nm → 451 nm → 357 nm for the 1–10 K fraction and of 376 nm → 464 nm for the >100 K fraction. The extent of the binding affinities exactly followed the sequential orders interpreted from the 2D-COS, and they exhibited the distinctive ranges of the logarithmic values from 5.86 to 4.91 and from 6.48 to 5.95 for the 1–10 K and the >100 K fractions, respectively. Our studies demonstrated that fluorescence quenching combined with 2D-COS could be successfully utilized to give insight into the chemical heterogeneity associated with metal-binding sites within the relatively homogeneous HA size fractions
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