7,338 research outputs found
K^*(BG) rings for groups of order 32
B. Schuster \cite{SCH1} proved that the 2 Morava -theory
is evenly generated for all groups of order 32. For the four
groups with the numbers 38, 39, 40 and 41 in the Hall-Senior list \cite{H},
the ring has been shown to be generated as a -module by
transferred Euler classes. In this paper, we show this for arbitrary and
compute the ring structure of . Namely, we show that
is the quotient of a polynomial ring in 6 variables over by an
ideal for which we list explicit generators.Comment: 23 page
A multi-wavelength observation and investigation of six infrared dark clouds
Context. Infrared dark clouds (IRDCs) are ubiquitous in the Milky Way, yet
they play a crucial role in breeding newly-formed stars.
Aims. With the aim of further understanding the dynamics, chemistry, and
evolution of IRDCs, we carried out multi-wavelength observations on a small
sample.
Methods. We performed new observations with the IRAM 30 m and CSO 10.4 m
telescopes, with tracers , HCN, , ,
DCO, SiO, and DCN toward six IRDCs G031.97+00.07, G033.69-00.01,
G034.43+00.24, G035.39-00.33, G038.95-00.47, and G053.11+00.05.
Results. We investigated 44 cores including 37 cores reported in previous
work and seven newly-identified cores. Toward the dense cores, we detected 6
DCO, and 5 DCN lines. Using pixel-by-pixel spectral energy distribution
(SED) fits of the 70 to 500 m, we obtained dust
temperature and column density distributions of the IRDCs. We found that emission has a strong correlation with the dust temperature and column
density distributions, while showed the weakest correlation. It
is suggested that is indeed a good tracer in very dense
conditions, but is an unreliable one, as it has a relatively
low critical density and is vulnerable to freezing-out onto the surface of cold
dust grains. The dynamics within IRDCs are active, with infall, outflow, and
collapse; the spectra are abundant especially in deuterium species.
Conclusions. We observe many blueshifted and redshifted profiles,
respectively, with and toward the same core. This
case can be well explained by model "envelope expansion with core collapse
(EECC)".Comment: 24 pages, 11 figures, 4 tables. To be published in A&A. The
resolutions of the pictures are cut dow
EEG–fMRI mapping of asymmetrical delta activity in a patient with refractory epilepsy is concordant with the epileptogenic region determined by intracranial EEG
We studied a patient with refractory focal epilepsy using continuous EEG-correlated fMRI. Seizures were characterized by head turning to the left and clonic jerking of the left arm, suggesting a right frontal epileptogenic region. Interictal EEG showed occasional runs of independent nonlateralized slow activity in the delta band with right frontocentral dominance and had no lateralizing value. Ictal scalp EEG had no lateralizing value. Ictal scalp EEG suggested right-sided central slow activity preceding some seizures. Structural 3-T MRI showed no abnormality. There was no clear epileptiform abnormality during simultaneous EEG–fMRI. We therefore modeled asymmetrical EEG delta activity at 1–3 Hz near frontocentral electrode positions. Significant blood oxygen level-dependent (BOLD) signal changes in the right superior frontal gyrus correlated with right frontal oscillations at 1–3 Hz but not at 4–7 Hz and with neither of the two frequency bands when derived from contralateral or posterior electrode positions, which served as controls. Motor fMRI activations with a finger-tapping paradigm were asymmetrical: they were more anterior for the left hand compared with the right and were near the aforementioned EEG-correlated signal changes. A right frontocentral perirolandic seizure onset was identified with a subdural grid recording, and electric stimulation of the adjacent contact produced motor responses in the left arm and after discharges. The fMRI localization of the left hand motor and the detected BOLD activation associated with modeled slow activity suggest a role for localization of the epileptogenic region with EEG–fMRI even in the absence of clear interictal discharges
WFPC2 Observations of Massive and Compact Young Star Clusters in M31
We present color magnitude diagrams of four blue massive and compact star
clusters in M31: G38, G44, G94, and G293. The diagrams of the four clusters
reveal a well-populated upper main sequence and various numbers of supergiants.
The U-B and B-V colors of the upper main sequence stars are used to determine
reddening estimates of the different lines of sight in the M31 disk. Reddening
values range from E(B-V) = 0.20 +/- 0.10 to 0.31 +/- 0.11. We statistically
remove field stars on the basis of completeness, magnitude and color. Isochrone
fits to the field-subtracted, reddening-corrected diagrams yield age estimates
ranging from 63 +/- 15 Myr to 160 +/- 60 Myr. Implications for the recent
evolution of the disk near NGC 206 are discussed.Comment: 17 pages, Latex, ApJ, in Pres
Distributed Optimal Frequency Control Considering a Nonlinear Network-Preserving Model
This paper addresses the distributed optimal frequency control of power
systems considering a network-preserving model with nonlinear power flows and
excitation voltage dynamics. Salient features of the proposed distributed
control strategy are fourfold: i) nonlinearity is considered to cope with large
disturbances; ii) only a part of generators are controllable; iii) no load
measurement is required; iv) communication connectivity is required only for
the controllable generators. To this end, benefiting from the concept of
'virtual load demand', we first design the distributed controller for the
controllable generators by leveraging the primal-dual decomposition technique.
We then propose a method to estimate the virtual load demand of each
controllable generator based on local frequencies. We derive incremental
passivity conditions for the uncontrollable generators. Finally, we prove that
the closed-loop system is asymptotically stable and its equilibrium attains the
optimal solution to the associated economic dispatch problem. Simulations,
including small and large-disturbance scenarios, are carried on the New England
system, demonstrating the effectiveness of our design
Role of electrostatic interactions in amyloid beta-protein (Abeta) oligomer formation: A discrete molecular dynamics study
Pathological folding and oligomer formation of the amyloid beta-protein
(Abeta) are widely perceived as central to Alzheimer's disease (AD).
Experimental approaches to study Abeta self-assembly are problematic, because
most relevant aggregates are quasi-stable and inhomogeneous. We apply a
discrete molecular dynamics (DMD) approach combined with a four-bead protein
model to study oligomer formation of the amyloid beta-protein (Abeta). We
address the differences between the two most common Abeta alloforms, Abeta40
and Abeta42, which oligomerize differently in vitro. We study how the presence
of electrostatic interactions (EIs) between pairs of charged amino acids
affects Abeta40 and Abeta42 oligomer formation. Our results indicate that EIs
promote formation of larger oligomers in both Abeta40 and Abeta42. The Abeta40
size distribution remains unimodal, whereas the Abeta42 distribution is
trimodal, as observed experimentally. Abeta42 folded structure is characterized
by a turn in the C-terminus that is not present in Abeta40. We show that the
same C-terminal region is also responsible for the strongest intermolecular
contacts in Abeta42 pentamers and larger oligomers. Our results suggest that
this C-terminal region plays a key role in the formation of Abeta42 oligomers
and the relative importance of this region increases in the presence of EIs.
These results suggest that inhibitors targeting the C-terminal region of
Abeta42 oligomers may be able to prevent oligomer formation or structurally
modify the assemblies to reduce their toxicity.Comment: Accepted for publication at Biophysical Journa
Non-universal Critical Quantities from Variational Perturbation Theory and Their Application to the BEC Temperature Shift
For an O(N) symmetric scalar field theory with Euclidean action integral d^3x
[1/2 |nabla phi|^2 + 1/2 r phi^2 + 1/4! u phi^4], where phi = (phi_1,...,phi_N)
is a vector of N real field components, variational perturbation theory through
seven loops is employed for N = 0,1,2,3,4 to compute the renormalized value of
r/(N+2)u^2 at the phase transition. Its exact large-N limit is determined as
well. We also extend an earlier computation of the interaction-induced shift
Delta/Nu for N = 1,2,4 to N = 0,3. For N = 2, the results for the two
quantities are used to compute the second-order shift of the condensation
temperature of a dilute Bose gas, both in the homogenous case and for the wide
limit of a harmonic trap. Our results are in agreement with earlier Monte Carlo
simulations for N = 1,2,4. The appendix contains previously unpublished
numerical seven-loop data provided to us by B.Nickel.Comment: 19 page
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