3,238 research outputs found
Spatial Selectivity and Binaural Responses in the Inferior Colliculus of the Great Horned Owl
In this study we have investigated the processing of auditory cues for sound localization in the great horned owl (Bubo virginianus). Previous studies have shown that the barn owl, whose ears are asymmetrically oriented in the vertical plane, has a 2-dimensional, topographic representation of auditory space in the external division of the inferior colliculus (ICx). As in the barn owl, the great horned owl's ICx is anatomically distinct and projects to the optic tectum. Neurons in ICx respond over only a small range of azimuths (mean = 32 degrees), and azimuth is topographically mapped. In contrast to the barn owl, the great horned owl has bilaterally symmetrical ears and its receptive fields are not restricted in elevation. The binaural cues available for sound localization were measured both with cochlear microphonic recordings and with a microphone attached to a probe tube in the auditory canal. Interaural time disparity (ITD) varied monotonically with azimuth. Interaural intensity differences (IID) also changed with azimuth, but the largest IIDs were less than 15 dB, and the variation was not monotonic. Neither ITD nor IID varied systematically with changes in the vertical position of a sound source. We used dichotic stimulation to determine the sensitivity of ICx neurons to these binaural cues. Best ITD of ICx units was topographically mapped and strongly correlated with receptive-field azimuth. The width of ITD tuning curves, measured at 50% of the maximum response, averaged 72 microseconds. All ICx neurons responded only to binaural stimulation and had nonmonotonic IID tuning curves. Best IID was weakly, but significantly, correlated with best ITD (r = 0.39, p less than 0.05). The IID tuning curves, however, were broad (mean 50% width = 24 dB), and 67% of the units had best IIDs within 5 dB of 0 dB IID. ITD tuning was sensitive to variations in IID in the direction opposite to that expected for time-intensity trading, but the magnitude of this effect was only 1.5 microseconds/dB IID. We conclude that, in the great horned owl, the spatial selectivity of ICx neurons arises primarily from their ITD tuning. Except for the absence of elevation selectivity and the narrow range of best IIDs, ICx in the great horned owl appears to be organized much the same as in the barn owl
Non(anti)commutative superspace with coordinate-dependent deformation
We consider non(anti)commutative superspace with coordinate dependent
deformation parameters . We show that a chiral
supersymmetry can be defined and that chiral and antichiral superfields are
still closed under the Moyal-Weyl associative product implementing the
deformation. A consistent Super Yang-Mills deformed theory can
be constructed provided satisfies a suitable condition which
can be connected with the graviphoton background at the origin of the
deformation. After adding matter we also discuss the Konishi anomaly and the
gluino condensation.Comment: References added. Accepted for publication in PR
Remarks on the analytic structure of supersymmetric effective actions
We study the effective superpotential of N=1 supersymmetric gauge theories
with a mass gap, whose analytic properties are encoded in an algebraic curve.
We propose that the degree of the curve equals the number of semiclassical
branches of the gauge theory. This is true for supersymmetric QCD with one
adjoint and polynomial superpotential, where the two sheets of its
hyperelliptic curve correspond to the gauge theory pseudoconfining and higgs
branches. We verify this proposal in the new case of supersymmetric QCD with
two adjoints and superpotential V(X)+XY^2, which is the confining phase
deformation of the D_{n+2} SCFT. This theory has three kinds of classical vacua
and its curve is cubic. Each of the three sheets of the curve corresponds to
one of the three semiclassical branches of the gauge theory. We show that one
can continuously interpolate between these branches by varying the couplings
along the moduli space.Comment: 49 pages, 3 figures, harvmac; typos correcte
Quivers via anomaly chains
We study quivers in the context of matrix models. We introduce chains of
generalized Konishi anomalies to write the quadratic and cubic equations that
constrain the resolvents of general affine and non-affine quiver gauge
theories, and give a procedure to calculate all higher-order relations. For
these theories we also evaluate, as functions of the resolvents, VEV's of
chiral operators with two and four bifundamental insertions. As an example of
the general procedure we explicitly consider the two simplest quivers A2 and
A1(affine), obtaining in the first case a cubic algebraic curve, and for the
affine theory the same equation as that of U(N) theories with adjoint matter,
successfully reproducing the RG cascade result.Comment: 32 pages, latex; typos corrected, published versio
Veneziano-Yankielowicz Superpotential Terms in N=1 SUSY Gauge Theories
The Veneziano-Yankielowicz glueball superpotential for an arbitrary N=1 SUSY
pure gauge theory with classical gauge group is derived using an approach
following recent work of Dijkgraaf, Vafa and others. These non-perturbative
terms, which had hitherto been included by hand in the above approach, are thus
seen to arise naturally, and the approach is rendered self-contained. By
minimising the glueball superpotential for theories with fundamental matter
added, the expected vacuum structure with gaugino condensation and chiral
symmetry breaking is obtained. Various possible extensions are also discussed.Comment: 9 page
Structure of Metastable States in Phase Transitions with High-Spin Low-Spin Degree of Freedom
Difference of degeneracy of the low-spin (LS) and high-spin (HS) states
causes interesting entropy effects on spin-crossover phase transitions and
charge transfer phase transitions in materials composed of the spin-crossover
atoms. Mechanisms of the spin-crossover (SC) phase transitions have been
studied by using Wajnflasz model, where the degeneracy of the spin states (HS
or LS) is taken into account and cooperative natures of the spin-crossover
phase transitions have been well described. Recently, a charge transfer (CT)
phase transition due to electron hopping between LS and HS sites has been
studied by using a generalized Wajnflasz model. In the both systems of SC and
CT, the systems have a high temperature structure (HT) and a low temperature
structure (LT), and the change between them can be a smooth crossover or a
discontinuous first order phase transition depending on the parameters of the
systems. Although apparently the standard SC system and the CT system are very
different, it is shown that both models are equivalent under a certain
transformation of variables. In both systems, the structure of metastable state
at low temperatures is a matter of interest. We study temperature dependence of
fraction of HT systematically in a unified model, and find several structures
of equilibrium and metastable states of the model as functions of system
parameters. In particular, we find a reentrant type metastable branch of HT in
a low temperature region, which would play an important role to study the
photo-irradiated processes of related materials.Comment: 19 pages, 11 figure
Chiral Rings, Anomalies and Electric-Magnetic Duality
We study electric-magnetic duality in the chiral ring of a supersymmetric
U(N_c) gauge theory with adjoint and fundamental matter, in presence of a
general confining phase superpotential for the adjoint and the mesons. We find
the magnetic solution corresponding to both the pseudoconfining and higgs
electric vacua. By means of the Dijkgraaf-Vafa method, we match the effective
glueball superpotentials and show that in some cases duality works exactly
offshell. We give also a picture of the analytic structure of the resolvents in
the magnetic theory, as we smoothly interpolate between different higgs vacua
on the electric side.Comment: 54 pages, harvmac. v2: typos correcte
Identification of proteolytic products as indicators of quality in ground and whole meat
This study was devoted to the identification of specific peptides and proteins which can serve as indicators of spoilage in meat. Samples of ground and whole meat were subjected to storage at 4C, at intervals of 0, 2, 4, 8, 12 and 16 days, samples were analyzed for pH and microbial populations and subjected to extraction and separation of individual sarcoplasmic and myofibrillar peptides and proteins by SDS (sodium dodecyl sulfate) and native electrophoresis and by RP-HPLC. Sarcoplasmic protein and peptide fractions from RP-HPLC were collected and identified by (electrospray ionization mass spectrometry) ESI-MS. The results demonstrated substantial differences in microbial population and pH between ground and whole meat during storage. Separation by SDS-electro-phoresis showed substantial changes in myofibrillar protein of ground meat after 12 days and of whole meat after 16 days of storage. Separation and identification of sarcoplasmic proteins by SDS-electrophoresis and by RP-HPLC followed by ESI-MS revealed the disappearance of a protein fraction band of MW 36 kDa after 8 days of storage in ground and whole meat
Algebraic Correlation Function and Anomalous Diffusion in the HMF model
In the quasi-stationary states of the Hamiltonian Mean-Field model, we
numerically compute correlation functions of momenta and diffusion of angles
with homogeneous initial conditions. This is an example, in a N-body
Hamiltonian system, of anomalous transport properties characterized by non
exponential relaxations and long-range temporal correlations. Kinetic theory
predicts a striking transition between weak anomalous diffusion and strong
anomalous diffusion. The numerical results are in excellent agreement with the
quantitative predictions of the anomalous transport exponents. Noteworthy, also
at statistical equilibrium, the system exhibits long-range temporal
correlations: the correlation function is inversely proportional to time with a
logarithmic correction instead of the usually expected exponential decay,
leading to weak anomalous transport properties
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