307 research outputs found
On the completability of incomplete orthogonal Latin rectangles
We address the problem of completability for 2-row orthogonal Latin rectangles (OLR2). Our approach is to identify all pairs of incomplete 2-row Latin rectangles that are not com- pletable to an OLR2 and are minimal with respect to this property; i.e., we characterize all circuits of the independence system associated with OLR2. Since there can be no poly- time algorithm generating the clutter of circuits of an arbitrary independence system, our work adds to the few independence systems for which that clutter is fully described. The result has a direct polyhedral implication; it gives rise to inequalities that are valid for the polytope associated with orthogonal Latin squares and thus planar multi-dimensional assign- ment. A complexity result is also at hand: completing a set of (n - 1) incomplete MOLR2 is NP-complete
Conjunctions of Among Constraints
Many existing global constraints can be encoded as a conjunction of among
constraints. An among constraint holds if the number of the variables in its
scope whose value belongs to a prespecified set, which we call its range, is
within some given bounds. It is known that domain filtering algorithms can
benefit from reasoning about the interaction of among constraints so that
values can be filtered out taking into consideration several among constraints
simultaneously. The present pa- per embarks into a systematic investigation on
the circumstances under which it is possible to obtain efficient and complete
domain filtering algorithms for conjunctions of among constraints. We start by
observing that restrictions on both the scope and the range of the among
constraints are necessary to obtain meaningful results. Then, we derive a
domain flow-based filtering algorithm and present several applications. In
particular, it is shown that the algorithm unifies and generalizes several
previous existing results.Comment: 15 pages plus appendi
Studies of Diffuse Interstellar Bands. V. Pairwise Correlations of Eight Strong DIBs and Neutral Hydrogen, Molecular Hydrogen, and Color Excess
We establish correlations between equivalent widths of eight diffuse
interstellar bands (DIBs), and examine their correlations with atomic hydrogen,
molecular hydrogen, and EB-V . The DIBs are centered at \lambda\lambda 5780.5,
6204.5, 6283.8, 6196.0, 6613.6, 5705.1, 5797.1, and 5487.7, in decreasing order
of Pearson\^as correlation coefficient with N(H) (here defined as the column
density of neutral hydrogen), ranging from 0.96 to 0.82. We find the equivalent
width of \lambda 5780.5 is better correlated with column densities of H than
with E(B-V) or H2, confirming earlier results based on smaller datasets. We
show the same is true for six of the seven other DIBs presented here. Despite
this similarity, the eight strong DIBs chosen are not well enough correlated
with each other to suggest they come from the same carrier. We further conclude
that these eight DIBs are more likely to be associated with H than with H2, and
hence are not preferentially located in the densest, most UV shielded parts of
interstellar clouds. We suggest they arise from different molecules found in
diffuse H regions with very little H (molecular fraction f<0.01). Of the 133
stars with available data in our study, there are three with significantly
weaker \lambda 5780.5 than our mean H-5780.5 relationship, all of which are in
regions of high radiation fields, as previously noted by Herbig. The
correlations will be useful in deriving interstellar parameters when direct
methods are not available. For instance, with care, the value of N(H) can be
derived from W{\lambda}(5780.5).Comment: Accepted for publication in The Astrophysical Journal; 37 pages, 11
figures, 6 table
The Rotational Excitation Temperature of the 6614 Diffuse Interstellar Band Carrier
Analysis of high spectral resolution observations of the 6614
diffuse interstellar band (DIB) line profile show systematic variations in the
positions of the peaks in the substructure of the profile. These variations --
shown here for the first time -- can be understood most naturally in the
framework of rotational contours of large molecules, where the variations are
caused by changes in the rotational excitation temperature. We show that the
rotational excitation temperature for the DIB carrier is likely significantly
lower than the gas kinetic temperature -- indicating that for this particular
DIB carrier angular momentum buildup is not very efficient.Comment: Accepted by ApJ Letters; 16 pages, 2 figure
Vegetation-based landscape regions of Hungary.
he first version of the map of the Hungarian vegetation-based landscape regions were prepared
at the scale of 1 : 200,000 (1 km or higher resolution). The primary goal of the map was
to provide an exact background for the presentation and evaluation of the data of theMĂTA
database. Secondly, we intended to give an up-to-date and detailed vegetation-based division
of Hungary with a comprehensive nomenclature of the regions. Regions were primarily defined on the basis of their present zonal vegetation, or their dominant extrazonal or
edaphic vegetation. Where this was not possible, abiotic factors that influence the potential
vegetation, the flora were taken into consideration, thus, political and economical factors
were ignored. All region borders were defined by local expert botanists, mainly based on
their field knowledge. The map differs in many features from the currently used, country-
wide, flora- or geography-based divisions in many features. We consider our map to be
temporary (i.e. a work map), and we plan to refine and improve it after 5 years of testing
Investigation of the deposition and emission of mercury in arctic snow during an atmospheric mercury depletion event
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94701/1/jgrd14741.pd
A coincidence between a hydrocarbon plasma absorption spectrum and the lambda 5450 DIB
The aim of this work is to link the broad lambda 5450 diffuse interstellar
band (DIB) to a laboratory spectrum recorded through an expanding acetylene
plasma. Cavity ring-down direct absorption spectra and astronomical
observations of HD 183143 with the HERMES spectrograph on the Mercator
Telescope in La Palma and the McKellar spectrograph on the DAO 1.2 m Telescope
are compared. In the 543-547 nm region a broad band is measured with a band
maximum at 545 nm and FWHM of 1.03(0.1) nm coinciding with a well-known diffuse
interstellar band at lambda 5450 with FWHM of 0.953 nm. A coincidence is found
between the laboratory and the two independent observational studies obtained
at higher spectral resolution. This result is important, as a match between a
laboratory spectrum and a - potentially lifetime broadened - DIB is found. A
series of additional experiments has been performed in order to unambiguously
identify the laboratory carrier of this band. This has not been possible. The
laboratory results, however, restrict the carrier to a molecular transient,
consisting of carbon and hydrogen.Comment: 6 pages, 3 figures, accepted for publication in A&
Symptom patterns in women with premenstrual syndrome complaints: a prospective assessment using a marker for ovulation and screening criteria for adequate ovarian function
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72929/1/j.1365-2648.1991.tb01727.x.pd
- âŠ