7,693 research outputs found
DDF and Pohlmeyer invariants of (super)string
We show how the Pohlmeyer invariants of the bosonic string are expressible in
terms of DDF invariants. Quantization of the DDF observables in the usual way
yields a consistent quantization of the algebra of Pohlmeyer invariants.
Furthermore it becomes straightforward to generalize the Pohlmeyer invariants
to the superstring as well as to all backgrounds which allow a free field
realization of the worldsheet theory.Comment: 17 pp, minor typos corrected, references to papers by Isaev and
Borodulin added, which contain essentially the same results as reported her
Relationship between Internal Consistency and Goodness of Fit Maximum Likelihood Factor Analysis with Varimax Rotation
This study investigates how reliability (internal consistency) affects model-fitting in maximum likelihood exploratory factor analysis (EFA). This was accomplished through an examination of goodness of fit indices between the population and the sample matrices. Monte Carlo simulations were performed to create pseudo-populations with known parameters. Results indicated that the higher the internal consistency the worse the fit. It is postulated that the observations are similar to those from structural equation modeling where a good fit with low correlations can be observed and also the reverse with higher item correlations
Nonlinear Volatility of River Flux Fluctuations
We study the spectral properties of the magnitudes of river flux increments,
the volatility. The volatility series exhibits (i) strong seasonal periodicity
and (ii) strongly power-law correlations for time scales less than one year. We
test the nonlinear properties of the river flux increment series by randomizing
its Fourier phases and find that the surrogate volatility series (i) has almost
no seasonal periodicity and (ii) is weakly correlated for time scales less than
one year. We quantify the degree of nonlinearity by measuring (i) the amplitude
of the power spectrum at the seasonal peak and (ii) the correlation power-law
exponent of the volatility series.Comment: 5 revtex pages, 6 page
Direct visualization reveals dynamics of a transient intermediate during protein assembly
Interactions between proteins underlie numerous biological functions. Theoretical work suggests that protein interactions initiate with formation of transient intermediates that subsequently relax to specific, stable complexes. However, the nature and roles of these transient intermediates have remained elusive. Here, we characterized the global structure, dynamics, and stability of a transient, on-pathway intermediate during complex assembly between the Signal Recognition Particle (SRP) and its receptor. We show that this intermediate has overlapping but distinct interaction interfaces from that of the final complex, and it is stabilized by long-range electrostatic interactions. A wide distribution of conformations is explored by the intermediate; this distribution becomes more restricted in the final complex and is further regulated by the cargo of SRP. These results suggest a funnel-shaped energy landscape for protein interactions, and they provide a framework for understanding the role of transient intermediates in protein assembly and biological regulation
Spatially Resolved Star Formation History Along the Disk of M82 Using Multi-Band Photometric Data
We present the results on the star formation history and extinction in the
disk of M82 over spatial scales of 10" (~180 pc). Multi-band photometric data
covering from the far ultraviolet to the near infrared bands were fitted to a
grid of synthetic spectral energy distributions. We obtained distribution
functions of age and extinction for each of the 117 apertures analyzed, taking
into account observational errors through Monte-Carlo simulations. These
distribution functions were fitted with gaussian functions to obtain the mean
ages and extinctions along with errors on them. The analyzed zones include the
high surface brightness complexes defined by O'Connell & Mangano (1978). We
found that these complexes share the same star formation history and extinction
as the field stellar populations in the disk. There is an indication that the
stellar populations are marginally older at the outer disk (450 Myr at ~3 kpc)
as compared to the inner disk (100 Myr at 0.5 kpc). For the nuclear regions
(radius less than 500 pc), we obtained an age of less than 10 Myr. The results
obtained in this work are consistent with the idea that the 0.5-3 kpc part of
the disk of M82 formed around 90% of the stellar mass in a star-forming episode
that started around 450 Myr ago lasting for about 350 Myr. We found that field
stars are the major contributors to the flux over the spatial scales analyzed
in this study, with stellar cluster contribution being 7% in the nucleus and
0.7% in the disk.Comment: 19 pages, 14 figures. Accepted for publication in The Astrophysical
Journa
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