23,731 research outputs found
Parameter estimation in a spatial unit root autoregressive model
Spatial unilateral autoregressive model is investigated in the
unit root case, that is when the parameters are on the boundary of the domain
of stability that forms a tetrahedron with vertices $(1,1,-1), \ (1,-1,1),\
(-1,1,1)(-1,-1,-1)nn^{3/2}$.Comment: 47 pages, 1 figur
A Stepwise [4 + 3] Cycloaddition Reaction of the 1,3-Diphenyl-2-azaallyl Anion
The 1,3-diphenyl-2-azaallyl anion (1) undergoes [3 + 2] cycloaddition reactions with the s-cis-fixed 1,3-dienes 8-11. In contrast, 1,1,2,2,3,3-hexamethyl-4,5-bis(methylene)cyclopentane (7) reacts with 1 to give the [4 + 3] cycloadduct 13 and the linear 1,4-addition product 14. This reaction is four orders of magnitude slower than the corresponding reaction of 1 with 1,2-bis(methylene)cyclopentane (8), which exclusively yields [3 + 2] cycloadducts. A change of mechanism - concerted cycloaddition of 8 and stepwise cycloaddition of 7 - is suggested, but not unequivocally proven. It is concluded that reactions of 1 with ordinary dienes cannot profit from concertedness by more than 5 kcal · mol-1
On the variances of a spatial unit root model
The asymptotic properties of the variances of the spatial autoregressive
model are investigated in the unit root case, that
is when the parameters are on the boundary of domain of stability that forms a
tetrahedron in . The limit of the variance of
is determined, where on the interior of the faces
of the domain of stability , on the edges , while on
the vertices
Biodiversity of estuarine fish faunas in West Africa
In West Africa (between Ivory Coast and Sénégal), estuarine environments vary from lagoons to high discharge rivers to inverse hypersaline estuaries. This results in a high diversity of estuarine fish species, with an important turnover and a core of ubiquitous species. The species richness of a given estuary depends on the combination of hydrological factors (marine or freshwater dominance) and biogeography (continental biogeographic regions). The catch rate is higher in lagoons and inverse estuaries than in normal estuaries, which can be explained by the predominance of small juveniles in the latter. Clupeids are the most abundant fishes all over the region, but different systems have different dominant species. Assessing the functioning of West-African estuaries provides useful comparisons to Asian estuarine systems
Strange particle production in a single-freeze-out model
The transverse-momentum spectra and elliptic flow of strange particles are
calculated in the framework of the single-freeze-out model and compared with
the recent RHIC data. An overall very good agreement between the model
predictions and the data is obtained.Comment: talk presented by WF during the VIIIth Int. Conf. on Strangeness in
Quark Matter, Cape Town, Sept. 15-20, 200
A Software Package for Neural Network Applications Development
Original Backprop (Version 1.2) is an MS-DOS package of four stand-alone C-language programs that enable users to develop neural network solutions to a variety of practical problems. Original Backprop generates three-layer, feed-forward (series-coupled) networks which map fixed-length input vectors into fixed length output vectors through an intermediate (hidden) layer of binary threshold units. Version 1.2 can handle up to 200 input vectors at a time, each having up to 128 real-valued components. The first subprogram, TSET, appends a number (up to 16) of classification bits to each input, thus creating a training set of input output pairs. The second subprogram, BACKPROP, creates a trilayer network to do the prescribed mapping and modifies the weights of its connections incrementally until the training set is leaned. The learning algorithm is the 'back-propagating error correction procedures first described by F. Rosenblatt in 1961. The third subprogram, VIEWNET, lets the trained network be examined, tested, and 'pruned' (by the deletion of unnecessary hidden units). The fourth subprogram, DONET, makes a TSR routine by which the finished product of the neural net design-and-training exercise can be consulted under other MS-DOS applications
J08069+1527: A newly discovered high amplitude, hybrid subdwarf B pulsator
We present our discovery of a new hybrid pulsating subdwarf B star,
J08069+1527. The effective temperature and surface gravity of 28,500400\,K
and 5.370.04\,dex, respectively, place this object inside the instability
strip and also among other pulsating hot subdwarfs of a hybrid nature, right
next to another fascinating star: Balloon\,090100001. From this proximity, we
anticipated this star could pulsate in both high and low frequency modes.
Indeed, our analysis of photometric data confirmed our prediction. We detected
two peaks in the high frequency region and two other peaks at low frequencies.
In addition, the amplitude of the dominant mode is very high and comparable to
the dominant peaks in other hybrid subdwarf B stars. Since this star is bright,
we performed time-series low resolution spectroscopy. Despite a low
signal-to-noise (S/N) ratio, we were able to detect the main peak from these
data. All our results strongly indicate that J08069+1527 is a high amplitude
pulsating hot subdwarf B star of hybrid nature. By analogy to the other
pulsating sdB star, we judge that the dominant mode we detected here has radial
nature. Future stellar modeling should provide us with quite good constrains as
p- and g-modes presented in this star are driven in different parts of its
interior.Comment: 7 pages, 10 figures, accepted for publication in MNRA
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