2,799 research outputs found
Cycles of length three and four in tournaments
Linial and Morgenstern conjectured that, among all -vertex tournaments
with cycles of length three, the number of cycles of length
four is asymptotically minimized by a random blow-up of a transitive tournament
with all but one part of equal size and one smaller part. We prove the
conjecture for by analyzing the possible spectrum of adjacency
matrices of tournaments. We also demonstrate that the family of extremal
examples is broader than expected and give its full description for
A spatially resolved pressure-based approach to evaluate combined effects of human activities and management in marine ecosystems
Optical Holonomic Quantum Computer
In this paper the idea of holonomic quantum computation is realized within
quantum optics. In a non-linear Kerr medium the degenerate states of laser
beams are interpreted as qubits. Displacing devices, squeezing devices and
interferometers provide the classical control parameter space where the
adiabatic loops are performed. This results into logical gates acting on the
states of the combined degenerate subspaces of the lasers, producing any one
qubit rotations and interactions between any two qubits. Issues such as
universality, complexity and scalability are addressed and several steps are
taken towards the physical implementation of this model.Comment: 16 pages, 3 figures, REVTE
Перспективи використання тонкодисперсних вуглецевих матеріалів
У останні десятиліття особливу увагу вчених привертає дослідження різних алотропних видозмін вуглецю, зокрема природних: алмазу, графіту, лонсдейліту, фулерену, вуглецевих нанотрубок (у тому числі шунгіту – природного нанотехн-логічного матеріалу) і штучних: карбіну, графену, аморфного вуглецю (кокс, вугілля, технічний вуглець, сажа, активоване вугілля). Водночас у техніці все більше розповсюдження отримують тонкодисперсні вуглецеві матеріали, зокрема тонкодисперсне вугілля та технічний вуглець, тонкоподрібнений аморфний вуглець, активоване вугілля, дослідженню яких присвячено ряд окремих досліджень, у т.ч. і авторів статті
Visually targeted reaching in horse-head grasshoppers
Visually targeted reaching to a specific object is a demanding neuronal task requiring the translation of the location of the object from a two-dimensionsal set of retinotopic coordinates to a motor pattern that guides a limb to that point in three-dimensional space. This sensorimotor transformation has been intensively studied in mammals, but was not previously thought to occur in animals with smaller nervous systems such as insects. We studied horse-head grasshoppers (Orthoptera: Proscopididae) crossing gaps and found that visual inputs are sufficient for them to target their forelimbs to a foothold on the opposite side of the gap. High-speed video analysis showed that these reaches were targeted accurately and directly to footholds at different locations within the visual field through changes in forelimb trajectory and body position, and did not involve stereotyped searching movements. The proscopids estimated distant locations using peering to generate motion parallax, a monocular distance cue, but appeared to use binocular visual cues to estimate the distance of nearby footholds. Following occlusion of regions of binocular overlap, the proscopids resorted to peering to target reaches even to nearby locations. Monocular cues were sufficient for accurate targeting of the ipsilateral but not the contralateral forelimb. Thus, proscopids are capable not only of the sensorimotor transformations necessary for visually targeted reaching with their forelimbs but also of flexibly using different visual cues to target reaches. © 2012 The Royal Society
An ALMA Survey of M-dwarfs in the Beta Pictoris Moving Group with Two New Debris Disc Detections
Previous surveys in the far-infrared have found very few, if any, M-dwarf
debris discs among their samples. It has been questioned whether M-dwarf discs
are simply less common than earlier types, or whether the low detection rate
derives from the wavelengths and sensitivities available to those studies. The
highly sensitive, long wavelength Atacama Large Millimetre/submillimetre Array
can shed light on the problem. This paper presents a survey of M-dwarf stars in
the young and nearby Beta Pictoris Moving Group with ALMA at Band 7
(880\,m). From the observational sample we detect two new sub-mm excesses
that likely constitute unresolved debris discs around GJ\,2006\,A and
AT\,Mic\,A and model distributions of the disc fractional luminosities and
temperatures. From the science sample of 36 M-dwarfs including AU\,Mic we find
a disc detection rate of 4/36 or 11.1\% that rises to
23.1\% when adjusted for completeness. We conclude that this
detection rate is consistent with the detection rate of discs around G and K
type stars and that the disc properties are also likely consistent with earlier
type stars. We additionally conclude that M-dwarf stars are not less likely to
host debris discs, but instead their detection requires longer wavelength and
higher sensitivity observations than have previously been employed.Comment: Accepted to MNRA
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