1,064 research outputs found
One-dimensional simulation of temperature and moisture in atmospheric and soil boundary layers
Meteorologists are interested in modeling the vertical flow of heat and moisture through the soil in order to better simulate the vertical and temporal variations of the atmospheric boundary layer. The one dimensional planetary boundary layer model of is modified by the addition of transport equations to be solved by a finite difference technique to predict soil moisture
Iterated lower bound formulas: a diagonalization-based approach to proof complexity
We propose a diagonalization-based approach to several important questions in proof complexity. We illustrate this approach in the context of the algebraic proof system IPS and in the context of propositional proof systems more generally. We use the approach to give an explicit sequence of CNF formulas {φn} such that VNP ≠ VP iff there are no polynomial-size IPS proofs for the formulas φn. This provides a natural equivalence between proof complexity lower bounds and standard algebraic complexity lower bounds. Our proof of this fact uses the implication from IPS lower bounds to algebraic complexity lower bounds due to Grochow and Pitassi together with a diagonalization argument: the formulas φn themselves assert the non-existence of short IPS proofs for formulas encoding VNP ≠ VP at a different input length. Our result also has meta-mathematical implications: it gives evidence for the difficulty of proving strong lower bounds for IPS within IPS. For any strong enough propositional proof system R, we define the *iterated R-lower bound formulas*, which inductively assert the non-existence of short R proofs for formulas encoding the same statement at a different input length, and propose them as explicit hard candidates for the proof system R. We observe that this hypothesis holds for Resolution following recent results of Atserias and Muller and of Garlik, and give evidence in favour of it for other proof systems
Local field potential measurement with low-power analog integrated circuit
Journal ArticleLocal field potentials (LFPs) in the brain are an important source of information for basic research and clinical (i.e., neuroprosthetic) applications. The energy contained in certain bands of LFPs in the 10-100 Hz range has been shown to correlate with specific arm movement parameters in nonhuman primates. In the near future, implantable devices will need to transmit neural information from hundreds of microelectrodes, and transcutaneous data transfer will become a significant bottleneck. Here we present a low-power, fully integrated circuit that performs on-site data reduction by isolating LFPs and measuring their signal energy. The resulting analog VLSI circuit consumes 586 μm × 79 μm of silicon area and dissipates only 5 nanowatts of power. We show that the chip performs similarly to state-of-the-art signal processing algorithms
Extreme events and event size fluctuations in biased random walks on networks
Random walk on discrete lattice models is important to understand various
types of transport processes. The extreme events, defined as exceedences of the
flux of walkers above a prescribed threshold, have been studied recently in the
context of complex networks. This was motivated by the occurrence of rare
events such as traffic jams, floods, and power black-outs which take place on
networks. In this work, we study extreme events in a generalized random walk
model in which the walk is preferentially biased by the network topology. The
walkers preferentially choose to hop toward the hubs or small degree nodes. In
this setting, we show that extremely large fluctuations in event-sizes are
possible on small degree nodes when the walkers are biased toward the hubs. In
particular, we obtain the distribution of event-sizes on the network. Further,
the probability for the occurrence of extreme events on any node in the network
depends on its 'generalized strength', a measure of the ability of a node to
attract walkers. The 'generalized strength' is a function of the degree of the
node and that of its nearest neighbors. We obtain analytical and simulation
results for the probability of occurrence of extreme events on the nodes of a
network using a generalized random walk model. The result reveals that the
nodes with a larger value of 'generalized strength', on average, display lower
probability for the occurrence of extreme events compared to the nodes with
lower values of 'generalized strength'
Engineering Functional Quantum Algorithms
Suppose that a quantum circuit with K elementary gates is known for a unitary
matrix U, and assume that U^m is a scalar matrix for some positive integer m.
We show that a function of U can be realized on a quantum computer with at most
O(mK+m^2log m) elementary gates. The functions of U are realized by a generic
quantum circuit, which has a particularly simple structure. Among other
results, we obtain efficient circuits for the fractional Fourier transform.Comment: 4 pages, 2 figure
In wild tobacco, Nicotiana attenuata, variation among bacterial communities of isogenic plants is mainly shaped by the local soil microbiota independently of the plants' capacity to produce jasmonic acid
The phytohormone jasmonic acid (JA) plays a central role in defense against necrotrophic pathogens and herbivores in Nicotiana attenuata. Recently Santhanam et al.(1) showed that JA does not have a major role in shaping the root- and shoot associated bacterial communities, though a few taxa differed among control (empty vector, EV) plants and plants impaired in their capacity to produce JA (irAOC). In this addendum, we provide additional data showing that the composition of the plant bacterial communities is mainly shaped by tissue type. The qualitative data analysis revealed that at the order level, 5 bacterial OTUs formed a core community found in all tissues irrespective of genotypes, while 9 OTUs were different among roots and shoots. The heterogeneity among individual plants was high masking the potential genotype effect on bacterial communities. Using a culture-dependent approach, 3 of 18 bacterial taxa retrieved either only from one of the genotypes or from both had a growth promoting effect on EV and irAOC seedlings. The data suggest that the local soil niche in which the roots grows is a major driver of the variability in root bacterial communities recruited by different individuals, and the plant growth-promoting effects of some taxa are independent of the genotype
Return interval distribution of extreme events and long term memory
The distribution of recurrence times or return intervals between extreme
events is important to characterize and understand the behavior of physical
systems and phenomena in many disciplines. It is well known that many physical
processes in nature and society display long range correlations. Hence, in the
last few years, considerable research effort has been directed towards studying
the distribution of return intervals for long range correlated time series.
Based on numerical simulations, it was shown that the return interval
distributions are of stretched exponential type. In this paper, we obtain an
analytical expression for the distribution of return intervals in long range
correlated time series which holds good when the average return intervals are
large. We show that the distribution is actually a product of power law and a
stretched exponential form. We also discuss the regimes of validity and perform
detailed studies on how the return interval distribution depends on the
threshold used to define extreme events.Comment: 8 pages, 6 figure
Studies on the growth of fishes in a brackishwater pen
The growth characteristics of fishes stocked in a pen of 100 sq. m. installed in the Pullavali brackishwater area were studied. The euryhaline species nf fish namely ehanos ehanos, Mugil sp., Siganus canaliculatus, Etroplus suratensis and Coranx sp. were stocked at the rate of 50 Nos. per sq. m. taking advantage of the free flow of water, rich in oxygen and plankton.
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