598 research outputs found
Entanglement of internal and external angular momenta of a single atom
We consider the exchange of spin and orbital angular momenta between a
circularly polarized Laguerre-Gaussian beam of light and a single atom trapped
in a two-dimensional harmonic potential. The radiation field is treated
classically but the atomic center-of-mass motion is quantized. The spin and
orbital angular momenta of the field are individually conserved upon
absorption, and this results in the entanglement of the internal and external
degrees of freedom of the atom. We suggest applications of this entanglement in
quantum information processing.Comment: 4 pages, 2 figure
Regulation of Heme Biosynthesis in Neurospora crassa
The mold Neurospora crassa does not accumulate porphyrins in iron deficiency but instead accumulates the sideramine desferricoprogen. In iron deficiency there is an accumulation of δ-aminolevulinic acid and the δ-aminolevulinic acid dehydratase level is very low. A similar situation exists in cobalt toxicity and zinc deficiency. The δ-aminolevulinic acid synthetase and ferroprotoporphyrin chelatase comparatively show only marginal changes under these conditions. Addition of iron and zinc to the respective metal-deficient cultures results in an induction of δ-aminolevulinic acid dehydratase. The induction of δ-aminolevulinic acid dehydratase is repressed by protoporphyrin and less effectively by hemin and hemoglobin. Iron deficiency, zinc deficiency, and cobalt toxicity have been found to interfere with the conversion of protoporphyrin into heme, thus rendering protoporphyrin available to repress the enzyme. This repression can be counteracted by iron and much more effectively by coprogen. A model has been proposed in which protoporphyrin has been visualized as the corepressor for the enzyme δ-aminolevulinic acid dehydratase. It is held that iron in the form of coprogen converts protoporphyrin to heme, the latter having a lesser affinity for the aporepressor. Coprogen can inhibit heme binding to the aporepressor and thus render the repressor nonfunctional. This will lead to a derepression of the enzyme δ-aminolevulinic acid dehydratase
Oxypred: prediction and classification of oxygen-binding proteins
This study describes a method for predicting and classifying oxygen-binding proteins. Firstly, support vector machine (SVM) modules were developed using amino acid composition and dipeptide composition for predicting oxygen-binding proteins, and achieved maximum accuracy of 85.5% and 87.8%, respectively. Secondly, an SVM module was developed based on amino acid composition, classifying the predicted oxygen-binding proteins into six classes with accuracy of 95.8%, 97.5%, 97.5%, 96.9%, 99.4%, and 96.0% for erythrocruorin, hemerythrin, hemocyanin, hemoglobin, leghemoglobin, and myoglobin proteins, respectively. Finally, an SVM module was developed using dipeptide composition for classifying the oxygen-binding proteins, and achieved maximum accuracy of 96.1%, 98.7%, 98.7%, 85.6%, 99.6%, and 93.3% for the above six classes, respectively. All modules were trained and tested by five-fold cross validation. Based on the above approach, a web server Oxypred was developed for predicting and classifying oxygen-binding proteins (available from http://www.imtech.res.in/raghava/oxypred/)
Cross-Document Pattern Matching
We study a new variant of the string matching problem called cross-document
string matching, which is the problem of indexing a collection of documents to
support an efficient search for a pattern in a selected document, where the
pattern itself is a substring of another document. Several variants of this
problem are considered, and efficient linear-space solutions are proposed with
query time bounds that either do not depend at all on the pattern size or
depend on it in a very limited way (doubly logarithmic). As a side result, we
propose an improved solution to the weighted level ancestor problem
Applications of carbon nanotubes in energy storage devices
The development of carbon nanotubes (CNTs) has contributed to the advancement in science and technology. If CNTs could be properly engineered, they can pave the way for the future development of numerous additional materials for a variety of purposes. The open and enriched chiral structure of CNTs enabled improvements in the properties and performances of other materials, when CNTs are incorporated in them. Depending on the structural and morphological requirements, CNTs have been incorporated in energy storage systems either as an additive to improve the electronic conductivity of cathode materials or as an active anode component. Furthermore, they have also been used directly as the electrode material in supercapacitors and fuel cells. Therefore, demand for CNTs is increasing due to their underlying properties and prospective applications in the energy storage research fields. Different types of CNTs are used in energy storage devices such as batteries, supercapacitors, fuel cells, and other devices. This chapter focuses on the review of CNTs in various energy conversion and storage systems, how their morphology and structure affect the electrochemical capabilities and energy storage methods
Learning Best Response Strategies for Agents in Ad Exchanges
Ad exchanges are widely used in platforms for online display advertising.
Autonomous agents operating in these exchanges must learn policies for
interacting profitably with a diverse, continually changing, but unknown
market. We consider this problem from the perspective of a publisher,
strategically interacting with an advertiser through a posted price mechanism.
The learning problem for this agent is made difficult by the fact that
information is censored, i.e., the publisher knows if an impression is sold but
no other quantitative information. We address this problem using the
Harsanyi-Bellman Ad Hoc Coordination (HBA) algorithm, which conceptualises this
interaction in terms of a Stochastic Bayesian Game and arrives at optimal
actions by best responding with respect to probabilistic beliefs maintained
over a candidate set of opponent behaviour profiles. We adapt and apply HBA to
the censored information setting of ad exchanges. Also, addressing the case of
stochastic opponents, we devise a strategy based on a Kaplan-Meier estimator
for opponent modelling. We evaluate the proposed method using simulations
wherein we show that HBA-KM achieves substantially better competitive ratio and
lower variance of return than baselines, including a Q-learning agent and a
UCB-based online learning agent, and comparable to the offline optimal
algorithm
The Tree Inclusion Problem: In Linear Space and Faster
Given two rooted, ordered, and labeled trees and the tree inclusion
problem is to determine if can be obtained from by deleting nodes in
. This problem has recently been recognized as an important query primitive
in XML databases. Kilpel\"ainen and Mannila [\emph{SIAM J. Comput. 1995}]
presented the first polynomial time algorithm using quadratic time and space.
Since then several improved results have been obtained for special cases when
and have a small number of leaves or small depth. However, in the worst
case these algorithms still use quadratic time and space. Let , , and
denote the number of nodes, the number of leaves, and the %maximum depth
of a tree . In this paper we show that the tree inclusion
problem can be solved in space and time: O(\min(l_Pn_T, l_Pl_T\log
\log n_T + n_T, \frac{n_Pn_T}{\log n_T} + n_{T}\log n_{T})). This improves or
matches the best known time complexities while using only linear space instead
of quadratic. This is particularly important in practical applications, such as
XML databases, where the space is likely to be a bottleneck.Comment: Minor updates from last tim
Locally Optimal Load Balancing
This work studies distributed algorithms for locally optimal load-balancing:
We are given a graph of maximum degree , and each node has up to
units of load. The task is to distribute the load more evenly so that the loads
of adjacent nodes differ by at most .
If the graph is a path (), it is easy to solve the fractional
version of the problem in communication rounds, independently of the
number of nodes. We show that this is tight, and we show that it is possible to
solve also the discrete version of the problem in rounds in paths.
For the general case (), we show that fractional load balancing
can be solved in rounds and discrete load
balancing in rounds for some function , independently of the
number of nodes.Comment: 19 pages, 11 figure
Development of a Neutron Source for Therapeutic Investigations
A collimated source is being developed for possible application to neutron therapy. The source is produced by the bombardment of 40 MeV alphas on a thick Be target. Using a tissue equivalent proportional counter, dose distributions were measured along the central and lateral axes. The quality of the radiation is estimated using dosimetric calculations
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