4,290 research outputs found
Balancing Bounded Treewidth Circuits
Algorithmic tools for graphs of small treewidth are used to address questions
in complexity theory. For both arithmetic and Boolean circuits, it is shown
that any circuit of size and treewidth can be
simulated by a circuit of width and size , where , if , and otherwise. For our main construction,
we prove that multiplicatively disjoint arithmetic circuits of size
and treewidth can be simulated by bounded fan-in arithmetic formulas of
depth . From this we derive the analogous statement for
syntactically multilinear arithmetic circuits, which strengthens a theorem of
Mahajan and Rao. As another application, we derive that constant width
arithmetic circuits of size can be balanced to depth ,
provided certain restrictions are made on the use of iterated multiplication.
Also from our main construction, we derive that Boolean bounded fan-in circuits
of size and treewidth can be simulated by bounded fan-in
formulas of depth . This strengthens in the non-uniform setting
the known inclusion that . Finally, we apply our
construction to show that {\sc reachability} for directed graphs of bounded
treewidth is in
A case of multiple fibroid uterus, complete placenta praevia, antepartum haemorrhage, myomectomy and obstetric hysterectomy: a near miss
An interesting case of young unbooked, unregistered, primigravida with multiple fibroid uterus, placenta praevia type IV, presented with APH in haemorrhagic Shock, impacted large fibroid in Lower Uterine Segment and Multiple fibroids on Anterior wall, fundus for which myomectomy was performed. Preterm Caesarean Section with extremely low birth weight infant delivered followed by life-saving Emergency Obstetric hysterectomy. She had uneventful recovery without any complications of massive transfusion or surgery. Case is being reported as an obstetric near miss
Dark Energy and the Statistical Study of the Observed Image Separations of the Multiply Imaged Systems in the CLASS Statistical Sample
The present day observations favour a universe which is flat, accelerated and
composed of matter (baryonic + dark) and of a negative
pressure component, usually referred to as dark energy or quintessence. The
Cosmic Lens All Sky Survey (CLASS), the largest radio-selected galactic mass
scale gravitational lens search project to date, has resulted in the largest
sample suitable for statistical analyses. In the work presented here, we
exploit observed image separations of the multiply imaged lensed radio sources
in the sample. We use two different tests: (1) image separation distribution
function of the lensed radio sources and (2)
{\dtheta}_{\mathrm{pred}} vs {\dtheta}_{\mathrm{obs}} as observational
tools to constrain the cosmological parameters and \Om. The results are
in concordance with the bounds imposed by other cosmological tests.Comment: 20 pages latex; Modified " Results and Discussion " section, new
references adde
The Bouncing Jet: A Newtonian Liquid Rebounding off a Free Surface
We find that a liquid jet can bounce off a bath of the same liquid if the
bath is moving horizontally with respect to the jet. Previous observations of
jets rebounding off a bath (e.g. Kaye effect) have been reported only for
non-Newtonian fluids, while we observe bouncing jets in a variety of Newtonian
fluids, including mineral oil poured by hand. A thin layer of air separates the
bouncing jet from the bath, and the relative motion replenishes the film of
air. Jets with one or two bounces are stable for a range of viscosity, jet flow
rate and velocity, and bath velocity. The bouncing phenomenon exhibits
hysteresis and multiple steady states.Comment: 9 pages, 7 figures. submitted to Physical Review
A New Lower Bound on the Maximum Number of Satisfied Clauses in Max-SAT and its Algorithmic Applications
A pair of unit clauses is called conflicting if it is of the form ,
. A CNF formula is unit-conflict free (UCF) if it contains no pair
of conflicting unit clauses. Lieberherr and Specker (J. ACM 28, 1981) showed
that for each UCF CNF formula with clauses we can simultaneously satisfy at
least \pp m clauses, where \pp =(\sqrt{5}-1)/2. We improve the
Lieberherr-Specker bound by showing that for each UCF CNF formula with
clauses we can find, in polynomial time, a subformula with clauses
such that we can simultaneously satisfy at least \pp m+(1-\pp)m'+(2-3\pp)n"/2
clauses (in ), where is the number of variables in which are not in
.
We consider two parameterized versions of MAX-SAT, where the parameter is the
number of satisfied clauses above the bounds and . The
former bound is tight for general formulas, and the later is tight for UCF
formulas. Mahajan and Raman (J. Algorithms 31, 1999) showed that every instance
of the first parameterized problem can be transformed, in polynomial time, into
an equivalent one with at most variables and clauses. We improve
this to variables and clauses. Mahajan and Raman
conjectured that the second parameterized problem is fixed-parameter tractable
(FPT). We show that the problem is indeed FPT by describing a polynomial-time
algorithm that transforms any problem instance into an equivalent one with at
most variables. Our results are obtained using our improvement
of the Lieberherr-Specker bound above
Doping effects in the coupled, two-leg spin ladder BiCu2PO6
We report preparation, x-ray diffraction, magnetic susceptibility chi(T) and
heat capacity Cp(T) measurements on the undoped samples as also samples with
Zn-doped (S = 0) at Cu site, Ni doped (S = 1) at Cu site, and Ca-doped (holes)
at Bi site in the coupled two-leg spin ladder system BiCu2PO6. While, Zn shows
complete solid solubility, Ni could be doped to about 20% and Ca to about 15%.
Magnetization and heat capacity data in the undoped compound point towards the
existence of frustration effects. In all the samples, the chi(T) at low
temperature increases with doping content. The Zn-induced susceptibility is
smaller than that due to effective S=1/2 moments possibly due to frustrating
next-nearest-neighbor interactions along the leg. For Zn content x > 0.01,
chi(T) deviates from the Curie-law at low temperatures. The magnetic specific
heat data Cm(T) for the Zn-doped samples show weak anomalies at low temperature
in agreement with chi(T) behavior. The anomalies are suggestive of spin
freezing at low-T. In contrast, prominent effects are observed in chi(T) and
Cm(T) on Ni-doped samples. The zero-field-cooled (ZFC) and field-cooled (FC)
chi(T) data are different from each other at low temperature unlike that for Zn
doped samples, clearly indicating a transition to a spin-glass like phase. No
anomalies were found in Ca- or Pb-doped samples.Comment: 16 pages, 9 figures, Submitted to J. Phy. Cond. Matte
CP violation in the decay mode
Within the framework of Standard Model, the exclusive decay mode is studied. Although the usual short distance contribution is
small compared to the similar mode, the process offers the
possibility of studying the CP violation, a feature absent in the
counterpart.Comment: 11 page latex file including 2 ps figures. Typos corrected, minor
changes. To appear in PR
- …