5,014 research outputs found
Malleable coding for updatable cloud caching
In software-as-a-service applications provisioned through cloud computing, locally cached data are often modified with updates from new versions. In some cases, with each edit, one may want to preserve both the original and new versions. In this paper, we focus on cases in which only the latest version must be preserved. Furthermore, it is desirable for the data to not only be compressed but to also be easily modified during updates, since representing information and modifying the representation both incur cost. We examine whether it is possible to have both compression efficiency and ease of alteration, in order to promote codeword reuse. In other words, we study the feasibility of a malleable and efficient coding scheme. The tradeoff between compression efficiency and malleability cost-the difficulty of synchronizing compressed versions-is measured as the length of a reused prefix portion. The region of achievable rates and malleability is found. Drawing from prior work on common information problems, we show that efficient data compression may not be the best engineering design principle when storing software-as-a-service data. In the general case, goals of efficiency and malleability are fundamentally in conflict.This work was supported in part by an NSF Graduate Research Fellowship (LRV), Grant CCR-0325774, and Grant CCF-0729069. This work was presented at the 2011 IEEE International Symposium on Information Theory [1] and the 2014 IEEE International Conference on Cloud Engineering [2]. The associate editor coordinating the review of this paper and approving it for publication was R. Thobaben. (CCR-0325774 - NSF Graduate Research Fellowship; CCF-0729069 - NSF Graduate Research Fellowship)Accepted manuscrip
Malleable Coding with Fixed Reuse
In cloud computing, storage area networks, remote backup storage, and similar
settings, stored data is modified with updates from new versions. Representing
information and modifying the representation are both expensive. Therefore it
is desirable for the data to not only be compressed but to also be easily
modified during updates. A malleable coding scheme considers both compression
efficiency and ease of alteration, promoting codeword reuse. We examine the
trade-off between compression efficiency and malleability cost-the difficulty
of synchronizing compressed versions-measured as the length of a reused prefix
portion. Through a coding theorem, the region of achievable rates and
malleability is expressed as a single-letter optimization. Relationships to
common information problems are also described
On palimpsests in neural memory: an information theory viewpoint
The finite capacity of neural memory and the
reconsolidation phenomenon suggest it is important to be able
to update stored information as in a palimpsest, where new
information overwrites old information. Moreover, changing
information in memory is metabolically costly. In this paper, we
suggest that information-theoretic approaches may inform the
fundamental limits in constructing such a memory system. In
particular, we define malleable coding, that considers not only
representation length but also ease of representation update,
thereby encouraging some form of recycling to convert an old
codeword into a new one. Malleability cost is the difficulty of
synchronizing compressed versions, and malleable codes are of
particular interest when representing information and modifying
the representation are both expensive. We examine the tradeoff
between compression efficiency and malleability cost, under a
malleability metric defined with respect to a string edit distance.
This introduces a metric topology to the compressed domain. We
characterize the exact set of achievable rates and malleability as
the solution of a subgraph isomorphism problem. This is all done
within the optimization approach to biology framework.Accepted manuscrip
A Novel Design of Multi-Chambered Biomass Battery
In this paper, a novel design of biomass battery has been introduced for providing electricity to meet the lighting requirements of rural household using biomass. A biomass battery is designed, developed and tested using cow dung as the raw material. This is done via anaerobic digestion of the cow dung, and power generation driven by the ions produced henceforth. The voltage and power output is estimated for the proposed system. It is for the first time that such a high voltage is obtained from cow dung fed biomass battery. The output characteristics of this novel battery design have also been compared with the previously designed battery
A stable Algebraic Spin Liquid in a Hubbard model
We show the existence of a stable Algebraic Spin Liquid (ASL) phase in a
Hubbard model defined on a honeycomb lattice with spin-dependent hopping that
breaks time-reversal symmetry. The effective spin model is the Kitaev model for
large on-site repulsion. The gaplessness of the emergent Majorana fermions is
protected by the time reversal (TR) invariance of this model. We prove that the
effective spin model is TR invariant in the entire Mott phase thus ensuring the
stability of the ASL. The model can be physically realized in cold atom systems
and we propose experimental signals of the ASL.Comment: Published in PR
Stronger instruments via integer programming in an observational study of late preterm birth outcomes
In an optimal nonbipartite match, a single population is divided into matched
pairs to minimize a total distance within matched pairs. Nonbipartite matching
has been used to strengthen instrumental variables in observational studies of
treatment effects, essentially by forming pairs that are similar in terms of
covariates but very different in the strength of encouragement to accept the
treatment. Optimal nonbipartite matching is typically done using network
optimization techniques that can be quick, running in polynomial time, but
these techniques limit the tools available for matching. Instead, we use
integer programming techniques, thereby obtaining a wealth of new tools not
previously available for nonbipartite matching, including fine and near-fine
balance for several nominal variables, forced near balance on means and optimal
subsetting. We illustrate the methods in our on-going study of outcomes of
late-preterm births in California, that is, births of 34 to 36 weeks of
gestation. Would lengthening the time in the hospital for such births reduce
the frequency of rapid readmissions? A straightforward comparison of babies who
stay for a shorter or longer time would be severely biased, because the
principal reason for a long stay is some serious health problem. We need an
instrument, something inconsequential and haphazard that encourages a shorter
or a longer stay in the hospital. It turns out that babies born at certain
times of day tend to stay overnight once with a shorter length of stay, whereas
babies born at other times of day tend to stay overnight twice with a longer
length of stay, and there is nothing particularly special about a baby who is
born at 11:00 pm.Comment: Published in at http://dx.doi.org/10.1214/12-AOAS582 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
AGRO-PESTICIDES AND ANDROLOGY
The extensive use of pesticides in agricultural practices has resulted in contamination of food and food resources. A number of animal species including humans have accumulated traces of pesticides through food chain. These toxic chemicals influence the physiology of numerous non-target species including man. The effects of many pesticides have been analyzed using in vivo and in vitro techniques and degenerative changes induced by the toxic chemicals have been reported even at nanomolar concentrations. The adverse effects on the male reproductive system include direct damage of the cells or disruption of the developmental pathways directly or through endocrine modifications. Toxic pesticides are known to cause Germ cells disintegration, loss of Leydig cells, atresia in Sertoli cell, degeneration of seminiferous tubules, alternation in spermatogenesis, depletion in semen quality, teratospermia and endocrine disruption. For ensuring pesticide free food and food supplements it is recommended that biological alternative should be explored to safeguard good health of plants, animals and humans
Simultaneously Sparse Solutions to Linear Inverse Problems with Multiple System Matrices and a Single Observation Vector
A linear inverse problem is proposed that requires the determination of
multiple unknown signal vectors. Each unknown vector passes through a different
system matrix and the results are added to yield a single observation vector.
Given the matrices and lone observation, the objective is to find a
simultaneously sparse set of unknown vectors that solves the system. We will
refer to this as the multiple-system single-output (MSSO) simultaneous sparsity
problem. This manuscript contrasts the MSSO problem with other simultaneous
sparsity problems and conducts a thorough initial exploration of algorithms
with which to solve it. Seven algorithms are formulated that approximately
solve this NP-Hard problem. Three greedy techniques are developed (matching
pursuit, orthogonal matching pursuit, and least squares matching pursuit) along
with four methods based on a convex relaxation (iteratively reweighted least
squares, two forms of iterative shrinkage, and formulation as a second-order
cone program). The algorithms are evaluated across three experiments: the first
and second involve sparsity profile recovery in noiseless and noisy scenarios,
respectively, while the third deals with magnetic resonance imaging
radio-frequency excitation pulse design.Comment: 36 pages; manuscript unchanged from July 21, 2008, except for updated
references; content appears in September 2008 PhD thesi
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