2,456 research outputs found
Properties of a beam splitter entangler with Gaussian input states
An explicit formula is given for the quantity of entanglement in the output
state of a beam splitter, given the squeezed vacuum states input in each mode.Comment: To appear in Phys. Rev.
SurfCon: Synonym Discovery on Privacy-Aware Clinical Data
Unstructured clinical texts contain rich health-related information. To
better utilize the knowledge buried in clinical texts, discovering synonyms for
a medical query term has become an important task. Recent automatic synonym
discovery methods leveraging raw text information have been developed. However,
to preserve patient privacy and security, it is usually quite difficult to get
access to large-scale raw clinical texts. In this paper, we study a new setting
named synonym discovery on privacy-aware clinical data (i.e., medical terms
extracted from the clinical texts and their aggregated co-occurrence counts,
without raw clinical texts). To solve the problem, we propose a new framework
SurfCon that leverages two important types of information in the privacy-aware
clinical data, i.e., the surface form information, and the global context
information for synonym discovery. In particular, the surface form module
enables us to detect synonyms that look similar while the global context module
plays a complementary role to discover synonyms that are semantically similar
but in different surface forms, and both allow us to deal with the OOV query
issue (i.e., when the query is not found in the given data). We conduct
extensive experiments and case studies on publicly available privacy-aware
clinical data, and show that SurfCon can outperform strong baseline methods by
large margins under various settings.Comment: KDD 2019 (Accepted for Oral Presentation at the Research track
Detecting the inseparability and distillability of continuous variable states in Fock space
The partial transposition(PT) operation is an effecient tool in detecting the
inseparability of a mixed state. We give an explicit formula for the PT
operation for the continuous variable states in Fock space. We then give the
necessary and sufficient condition for the positivity of Gaussian operators.
Based on this, a number of creterions on the inseparability and distillability
for the multimode Gaussian states are naturally drawn. We finally give an
explicit formula for the state in a subspace of a global Gaussian state. This
formula, together with the known results for Gaussian states, gives the
criterions for the inseparability and distillability in a subspace of the
global Gaussian state.Comment: 8 pages, no figure, some typing errors correcte
Do crystal structures obviate the need for theoretical models of GPCRs for structure-based virtual screening?
Recent highly expected structural characterizations of agonist-bound and antagonist-bound beta-2 adrenoreceptor (β2AR) by X-ray crystallography have been widely regarded as critical advances to enable more effective structure-based discovery of GPCRs ligands. It appears that this very important development may have undermined many previous efforts to develop 3D theoretical models of GPCRs. To address this question directly we have compared several historical β2AR models versus the inactive state and nanobody-stabilized active state of β2AR crystal structures in terms of their structural similarity and effectiveness of use in virtual screening for β2AR specific agonists and antagonists. Theoretical models, incluing both homology and de novo types, were collected from five different groups who have published extensively in the field of GPCRs modeling; all models were built before X-ray structures became available. In general, β2AR theoretical models differ significantly from the crystal structure in terms of TMH definition and the global packing. Nevertheless, surprisingly, several models afforded hit rates resulting from virtual screening of large chemical library enriched by known β2AR ligands that exceeded those using X-ray structures; the hit rates were particularly higher for agonists. Furthemore, the screening performance of models is associated with local structural quality such as the RMSDs for binding pocket residues and the ability to capture accurately most if not all critical protein/ligand interactions. These results suggest that carefully built models of GPCRs could capture critical chemical and structural features of the binding pocket thus may be even more useful for practical structure-based drug discovery than X-ray structures
Application of Quantitative Structure–Activity Relationship Models of 5-HT 1A Receptor Binding to Virtual Screening Identifies Novel and Potent 5-HT 1A Ligands
The 5-hydroxytryptamine 1A (5-HT1A) serotonin receptor has been an attractive target for treating mood and anxiety disorders such as schizophrenia. We have developed binary classification quantitative structure–activity relationship (QSAR) models of 5-HT1A receptor binding activity using data retrieved from the PDSP Ki database. The prediction accuracy of these models was estimated by external 5-fold cross-validation as well as using an additional validation set comprising 66 structurally distinct compounds from the World of Molecular Bioactivity database. These validated models were then used to mine three major types of chemical screening libraries, i.e., drug-like libraries, GPCR targeted libraries, and diversity libraries, to identify novel computational hits. The five best hits from each class of libraries were chosen for further experimental testing in radioligand binding assays, and nine of the 15 hits were confirmed to be active experimentally with binding affinity better than 10 μM. The most active compound, Lysergol, from the diversity library showed very high binding affinity (Ki) of 2.3 nM against 5-HT1A receptor. The novel 5-HT1A actives identified with the QSAR-based virtual screening approach could be potentially developed as novel anxiolytics or potential antischizophrenic drugs
Spectral function and quasiparticle weight in the generalized t-J model
We extend to the spectral function an approach which allowed us to calculate
the quasiparticle weight for destruction of a real electron Z_c sigma (k) (in
contrast to that of creation of a spinless holon Z_h(k) in a generalized
model, using the self-consistent Born approximation (SCBA). We compare our
results with those obtained using the alternative approach of Sushkov et al.,
which also uses the SCBA. The results for Z_c sigma (k) are also compared with
results obtained using the string picture and with exact diagonalizations of a
32-site square cluster. While on a qualitative level, all results look similar,
our SCBA approach seems to compare better with the ED one. The effect of
hopping beyond nearest neighbors, and that of the three-site term are
discussed.Comment: 7 pages, 6 figure
Phase-covariant quantum cloning of qudits
We study the phase-covariant quantum cloning machine for qudits, i.e. the
input states in d-level quantum system have complex coefficients with arbitrary
phase but constant module. A cloning unitary transformation is proposed. After
optimizing the fidelity between input state and single qudit reduced density
opertor of output state, we obtain the optimal fidelity for 1 to 2
phase-covariant quantum cloning of qudits and the corresponding cloning
transformation.Comment: Revtex, 6 page
Purity of Gaussian states: measurement schemes and time-evolution in noisy channels
We present a systematic study of the purity for Gaussian states of
single-mode continuous variable systems. We prove the connection of purity to
observable quantities for these states, and show that the joint measurement of
two conjugate quadratures is necessary and sufficient to determine the purity
at any time. The statistical reliability and the range of applicability of the
proposed measurement scheme is tested by means of Monte Carlo simulated
experiments. We then consider the dynamics of purity in noisy channels. We
derive an evolution equation for the purity of general Gaussian states both in
thermal and squeezed thermal baths. We show that purity is maximized at any
given time for an initial coherent state evolving in a thermal bath, or for an
initial squeezed state evolving in a squeezed thermal bath whose asymptotic
squeezing is orthogonal to that of the input state.Comment: 9 Pages, 6 Figures; minor errors correcte
Structural Learning of Attack Vectors for Generating Mutated XSS Attacks
Web applications suffer from cross-site scripting (XSS) attacks that
resulting from incomplete or incorrect input sanitization. Learning the
structure of attack vectors could enrich the variety of manifestations in
generated XSS attacks. In this study, we focus on generating more threatening
XSS attacks for the state-of-the-art detection approaches that can find
potential XSS vulnerabilities in Web applications, and propose a mechanism for
structural learning of attack vectors with the aim of generating mutated XSS
attacks in a fully automatic way. Mutated XSS attack generation depends on the
analysis of attack vectors and the structural learning mechanism. For the
kernel of the learning mechanism, we use a Hidden Markov model (HMM) as the
structure of the attack vector model to capture the implicit manner of the
attack vector, and this manner is benefited from the syntax meanings that are
labeled by the proposed tokenizing mechanism. Bayes theorem is used to
determine the number of hidden states in the model for generalizing the
structure model. The paper has the contributions as following: (1)
automatically learn the structure of attack vectors from practical data
analysis to modeling a structure model of attack vectors, (2) mimic the manners
and the elements of attack vectors to extend the ability of testing tool for
identifying XSS vulnerabilities, (3) be helpful to verify the flaws of
blacklist sanitization procedures of Web applications. We evaluated the
proposed mechanism by Burp Intruder with a dataset collected from public XSS
archives. The results show that mutated XSS attack generation can identify
potential vulnerabilities.Comment: In Proceedings TAV-WEB 2010, arXiv:1009.330
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