4,119 research outputs found
Regulation of Arabidopsis 14-3-3 gene expression by GABA.
The function in plants of the non-protein amino acid, gamma-aminobutyric acid (GABA) is poorly understood. In this study, we show that GABA down-regulates the expression of a large sub-set of 14-3-3 gene family members in Arabidopsis thaliana seedlings in a calcium, ethylene and abscisic acid-dependent manner. Gene expression is not affected when seedlings are supplied with glutamate, a precursor of GABA. The repression of 14-3-3 gene expression by GABA is dependent on functional ethylene and abscisic acid signalling pathways, since the response is lost in the etr1-1, abi1-1 and abi2-1 mutants. Calcium measurements show that in contrast to glutamate, GABA does not elicit a cytoplasmic calcium elevation, suggesting that the GABA response is unlikely to be mediated by glutamate receptors, as has been suggested previously. We suggest that in addition to its role as a stress-related metabolite, GABA may regulate gene expression in Arabidopsis, including members of the 14-3-3 gene family
Alignment based Network Coding for Two-Unicast-Z Networks
In this paper, we study the wireline two-unicast-Z communication network over
directed acyclic graphs. The two-unicast-Z network is a two-unicast network
where the destination intending to decode the second message has apriori side
information of the first message. We make three contributions in this paper:
1. We describe a new linear network coding algorithm for two-unicast-Z
networks over directed acyclic graphs. Our approach includes the idea of
interference alignment as one of its key ingredients. For graphs of a bounded
degree, our algorithm has linear complexity in terms of the number of vertices,
and polynomial complexity in terms of the number of edges.
2. We prove that our algorithm achieves the rate-pair (1, 1) whenever it is
feasible in the network. Our proof serves as an alternative, albeit restricted
to two-unicast-Z networks over directed acyclic graphs, to an earlier result of
Wang et al. which studied necessary and sufficient conditions for feasibility
of the rate pair (1, 1) in two-unicast networks.
3. We provide a new proof of the classical max-flow min-cut theorem for
directed acyclic graphs.Comment: The paper is an extended version of our earlier paper at ITW 201
The benefits of coding over routing in a randomized setting
A novel randomized network coding approach for robust, distributed transmission and compression of information in networks is presented, and its advantages over routing-based approaches is demonstrated
Alien Registration- Gaunce, Muriel R. (Fairfield, Somerset County)
https://digitalmaine.com/alien_docs/9539/thumbnail.jp
Guessing a password over a wireless channel (on the effect of noise non-uniformity)
A string is sent over a noisy channel that erases some of its characters.
Knowing the statistical properties of the string's source and which characters
were erased, a listener that is equipped with an ability to test the veracity
of a string, one string at a time, wishes to fill in the missing pieces. Here
we characterize the influence of the stochastic properties of both the string's
source and the noise on the channel on the distribution of the number of
attempts required to identify the string, its guesswork. In particular, we
establish that the average noise on the channel is not a determining factor for
the average guesswork and illustrate simple settings where one recipient with,
on average, a better channel than another recipient, has higher average
guesswork. These results stand in contrast to those for the capacity of wiretap
channels and suggest the use of techniques such as friendly jamming with
pseudo-random sequences to exploit this guesswork behavior.Comment: Asilomar Conference on Signals, Systems & Computers, 201
Byzantine modification detection in multicast networks using randomized network coding
Distributed randomized network coding, a robust approach to multicasting in distributed network settings, can be extended to provide Byzantine modification detection without the use of cryptographic functions is presented in this paper
Byzantine Modification Detection in Multicast Networks With Random Network Coding
An information-theoretic approach for detecting Byzantine or adversarial modifications in networks employing random linear network coding is described. Each exogenous source packet is augmented with a flexible number of hash symbols that are obtained as a polynomial function of the data symbols. This approach depends only on the adversary not knowing the random coding coefficients of all other packets received by the sink nodes when designing its adversarial packets. We show how the detection probability varies with the overhead (ratio of hash to data symbols), coding field size, and the amount of information unknown to the adversary about the random code
Confident decoding with GRAND
We establish that during the execution of any Guessing Random Additive Noise
Decoding (GRAND) algorithm, an interpretable, useful measure of decoding
confidence can be evaluated. This measure takes the form of a log-likelihood
ratio (LLR) of the hypotheses that, should a decoding be found by a given
query, the decoding is correct versus its being incorrect. That LLR can be used
as soft output for a range of applications and we demonstrate its utility by
showing that it can be used to confidently discard likely erroneous decodings
in favor of returning more readily managed erasures. As an application, we show
that feature can be used to compromise the physical layer security of short
length wiretap codes by accurately and confidently revealing a proportion of a
communication when code-rate is above capacity
Hiding Symbols and Functions: New Metrics and Constructions for Information-Theoretic Security
We present information-theoretic definitions and results for analyzing
symmetric-key encryption schemes beyond the perfect secrecy regime, i.e. when
perfect secrecy is not attained. We adopt two lines of analysis, one based on
lossless source coding, and another akin to rate-distortion theory. We start by
presenting a new information-theoretic metric for security, called symbol
secrecy, and derive associated fundamental bounds. We then introduce
list-source codes (LSCs), which are a general framework for mapping a key
length (entropy) to a list size that an eavesdropper has to resolve in order to
recover a secret message. We provide explicit constructions of LSCs, and
demonstrate that, when the source is uniformly distributed, the highest level
of symbol secrecy for a fixed key length can be achieved through a construction
based on minimum-distance separable (MDS) codes. Using an analysis related to
rate-distortion theory, we then show how symbol secrecy can be used to
determine the probability that an eavesdropper correctly reconstructs functions
of the original plaintext. We illustrate how these bounds can be applied to
characterize security properties of symmetric-key encryption schemes, and, in
particular, extend security claims based on symbol secrecy to a functional
setting.Comment: Submitted to IEEE Transactions on Information Theor
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