391 research outputs found
Misère quotients for impartial games
AbstractWe announce misère-play solutions to several previously-unsolved combinatorial games. The solutions are described in terms of misère quotients—commutative monoids that encode the additive structure of specific misère-play games. We also introduce several advances in the structure theory of misère quotients, including a connection between the combinatorial structure of normal and misère play
Simple 1-mm receivers with fixed tuned double sideband SIS mixer and wideband InP MMIC amplifier
We report on attempts to broaden the IF bandwidth of the BIMA 1mm SIS receivers by cascading fixed tuned double-sideband (DSB) SIS mixers and wideband MMIC IF amplifiers. To obtain the flattest receiver gain across the IF band we tested three schemes for keeping the mixer and amplifier as electrically close as possible. In Receiver I, we connected separate mixer and MMIC modules by a 1" stainless steel SMA elbow. In Receiver II, we integrated mixer and MMIC into a modified BIMA mixer module. In Receiver III, we devised a thermally split block where mixer and MMIC can be maintained at different temperatures in the same module. The best average receiver noise we achieved by combining SIS mixer and MMIC amplifier is 45 -50 K DSB for ν_(LO) = 215 - 240 GHz and below 80 K DSB for ν_(LO) = 205 - 270 GHz. The receiver noise can be made reasonably flat over the CARMA IF band (ν_(IF) = 1 - 5 GHz). Noise temperatures for all three receivers are comparable to or better than those obtained with the BIMA receiver
Organizational learning and emotion: constructing collective meaning in support of strategic themes
Missing in the organizational learning literature is an integrative framework that reflects the emotional as well as the cognitive dynamics involved. Here, we take a step in this direction by focusing in depth over time (five years) on a selected organization which manufactures electronic equipment for the office industry. Drawing on personal construct theory, we define organizational learning as the collective re-construal of meaning in the direction of strategically significant themes. We suggest that emotions arise as members reflect on progress or lack of progress in achieving organizational learning. Our evidence suggests that invalidation – where organizational learning fails to correspond with expectations – gives rise to anxiety and frustration, while validation – where organizational learning is aligned with or exceeds expectations – evokes comfort or excitement. Our work aims to capture the key emotions involved as organizational learning proceeds
Simple 1-mm receivers with fixed tuned double sideband SIS mixer and wideband InP MMIC amplifier
We report on attempts to broaden the IF bandwidth of the BIMA 1mm SIS receivers by cascading fixed tuned double-sideband (DSB) SIS mixers and wideband MMIC IF amplifiers. To obtain the flattest receiver gain across the IF band we tested three schemes for keeping the mixer and amplifier as electrically close as possible. In Receiver I, we connected separate mixer and MMIC modules by a 1" stainless steel SMA elbow. In Receiver II, we integrated mixer and MMIC into a modified BIMA mixer module. In Receiver III, we devised a thermally split block where mixer and MMIC can be maintained at different temperatures in the same module. The best average receiver noise we achieved by combining SIS mixer and MMIC amplifier is 45 -50 K DSB for ν_(LO) = 215 - 240 GHz and below 80 K DSB for ν_(LO) = 205 - 270 GHz. The receiver noise can be made reasonably flat over the CARMA IF band (ν_(IF) = 1 - 5 GHz). Noise temperatures for all three receivers are comparable to or better than those obtained with the BIMA receiver
A line confusion limited millimeter survey of Orion KL. II: Silicon-bearing species
We present a study of the Silicon-bearing species detected in a line
confusion limited survey towards Orion KL performed with the IRAM 30-m
telescope, which ranges from 80 to 280 GHz. Our aim is to derive physical and
chemical conditions for each family taking into account all observed lines from
all isotopologues of each species. We have modeled the lines of the detected
molecules using a radiative transfer code, which permit us to choose between
LVG and LTE approximations depending on the physical conditions of the gas. We
have used appropriate collisional rates for the LVG calculations. For the v=1
state of SiO we have detected the J=2-1 line and, for the first time in this
source, emission in the J=4-3 transition, both of them showing strong masering
effect. For SiO v=0, we have detected 28SiO, 29SiO, and 30SiO; in addition, we
have mapped the J = 5-4 SiO line. For SiS, we have detected the main species,
29SiS, and SiS v=1. Unlikely other species detected in Orion KL (IRc2), the
emission peak of SiS appears at a velocity of ~15.5 km s-1; a study of the 5-4
SiO line around IRc2 shows this feature as an extended component that probably
arises from the interaction of the outflow with the ambient cloud. We derive a
SiO/SiS column density ratio of ~13 in the plateau component. Besides, we
provide upper limits to the column density of several non-detected
Silicon-bearing species. The results of our chemical models show that while it
is possible to reproduce SiO in the gas phase (as well as on the grains), SiS
is a product of surface reactions, most likely involving direct reactions of S
with Si.Comment: Astronomy and Astrophysics, in pres
Giant Molecular Clouds in M33 - I. BIMA All Disk Survey
We present the first interferometric CO(J=1->0) map of the entire H-alpha
disk of M33. The 13" diameter synthesized beam corresponds to a linear
resolution of 50 pc, sufficient to distinguish individual giant molecular
clouds (GMCs). From these data we generated a catalog of 148 GMCs with an
expectation that no more than 15 of the sources are spurious. The catalog is
complete down to GMC masses of 1.5 X 10^5 M_sun and contains a total mass of
2.3 X 10^7 M_sun. Single dish observations of CO in selected fields imply that
our survey detects ~50% of the CO flux, hence that the total molecular mass of
M33 is 4.5 X 10^7 M_sun, approximately 2% of the HI mass. The GMCs in our
catalog are confined largely to the central region (R < 4 kpc). They show a
remarkable spatial and kinematic correlation with overdense HI filaments; the
geometry suggests that the formation of GMCs follows that of the filaments. The
GMCs exhibit a mass spectrum dN/dM ~ M^(-2.6 +/- 0.3), considerably steeper
than that found in the Milky Way and in the LMC. Combined with the total mass,
this steep function implies that the GMCs in M33 form with a characteristic
mass of 7 X 10^4 M_sun. More than 2/3 of the GMCs have associated HII regions,
implying that the GMCs have a short quiescent period. Our results suggest the
rapid assembly of molecular clouds from atomic gas, with prompt onset of
massive star formation.Comment: 19 pages, Accepted for Publication in the Astrophysical Journal
Supplemen
Testing Magnetic Field Models for the Class 0 Protostar L1527
For the Class 0 protostar, L1527, we compare 131 polarization vectors from
SCUPOL/JCMT, SHARP/CSO and TADPOL/CARMA observations with the corresponding
model polarization vectors of four ideal-MHD, non-turbulent, cloud core
collapse models. These four models differ by their initial magnetic fields
before collapse; two initially have aligned fields (strong and weak) and two
initially have orthogonal fields (strong and weak) with respect to the rotation
axis of the L1527 core. Only the initial weak orthogonal field model produces
the observed circumstellar disk within L1527. This is a characteristic of
nearly all ideal-MHD, non-turbulent, core collapse models. In this paper we
test whether this weak orthogonal model also has the best agreement between its
magnetic field structure and that inferred from the polarimetry observations of
L1527. We found that this is not the case; based on the polarimetry
observations the most favored model of the four is the weak aligned model.
However, this model does not produce a circumstellar disk, so our result
implies that a non-turbulent, ideal-MHD global collapse model probably does not
represent the core collapse that has occurred in L1527. Our study also
illustrates the importance of using polarization vectors covering a large area
of a cloud core to determine the initial magnetic field orientation before
collapse; the inner core magnetic field structure can be highly altered by a
collapse and so measurements from this region alone can give unreliable
estimates of the initial field configuration before collapse.Comment: 43 pages, 9 figures, 4 tables. Accepted by the Astrophysical Journa
Tracing the Bipolar Outflow from Orion Source I
Using CARMA, we imaged the 87 GHz SiO v=0 J=2-1 line toward Orion-KL with
0.45 arcsec angular resolution. The maps indicate that radio source I drives a
bipolar outflow into the surrounding molecular cloud along a NE--SW axis, in
agreement with the model of Greenhill et al. (2004). The extended high velocity
outflow from Orion-KL appears to be a continuation of this compact outflow.
High velocity gas extends farthest along a NW--SE axis, suggesting that the
outflow direction changes on time scales of a few hundred years.Comment: 4 pages, 4 figures; accepted for publication in Ap J Letter
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