2,953 research outputs found
Optimal two-qubit gate for generation of random bipartite entanglement
We numerically study protocols consisting of repeated applications of two
qubit gates used for generating random pure states. A necessary number of steps
needed in order to generate states displaying bipartite entanglement typical of
random states is obtained. For generic two qubit entangling gate the decay rate
of purity is found to scale as and therefore of order steps
are necessary to reach random bipartite entanglement. We also numerically
identify the optimal two qubit gate for which the convergence is the fastest.
Perhaps surprisingly, applying the same good two qubit gate in addition to a
random single qubit rotations at each step leads to a faster generation of
entanglement than applying a random two qubit transformation at each step.Comment: 9 pages, 9 PS figures; published versio
Topological interactions in systems of mutually interlinked polymer rings
The topological interaction arising in interlinked polymeric rings such as
DNA catenanes is considered. More specifically, the free energy for a pair of
linked random walk rings is derived where the distance between two segments
each of which is part of a different ring is kept constant. The topology
conservation is imposed by the Gauss invariant. A previous approach (M.Otto,
T.A. Vilgis, Phys.Rev.Lett. {\bf 80}, 881 (1998)) to the problem is refined in
several ways. It is confirmed, that asymptotically, i.e. for large
where is average size of single random walk ring, the effective
topological interaction (free energy) scales .Comment: 16 pages, 3 figur
The Convergence of Digital-Libraries and the Peer-Review Process
Pre-print repositories have seen a significant increase in use over the past
fifteen years across multiple research domains. Researchers are beginning to
develop applications capable of using these repositories to assist the
scientific community above and beyond the pure dissemination of information.
The contribution set forth by this paper emphasizes a deconstructed publication
model in which the peer-review process is mediated by an OAI-PMH peer-review
service. This peer-review service uses a social-network algorithm to determine
potential reviewers for a submitted manuscript and for weighting the relative
influence of each participating reviewer's evaluations. This paper also
suggests a set of peer-review specific metadata tags that can accompany a
pre-print's existing metadata record. The combinations of these contributions
provide a unique repository-centric peer-review model that fits within the
widely deployed OAI-PMH framework.Comment: Journal of Information Science [in press
Statistical mechanics of semiflexible ribbon polymers
The statistical mechanics of a ribbon polymer made up of two semiflexible
chains is studied using both analytical techniques and simulation. The system
is found to have a crossover transition at some finite temperature, from a type
of short range order to a fundamentally different sort of short range order. In
the high temperature regime, the 2-point correlation functions of the object
are identical to worm-like chains, while in the low temperature regime they are
different due to a twist structure. The crossover happens when the persistence
length of individual strands becomes comparable to the thickness of the ribbon.
In the low temperature regime, the ribbon is observed to have a novel
``kink-rod'' structure with a mutual exclusion of twist and bend in contrast to
smooth worm-like chain behaviour. This is due to its anisotropic rigidity and
corresponds to an {\it infinitely} strong twist-bend coupling. The
double-stranded polymer is also studied in a confined geometry. It is shown
that when the polymer is restricted in a particular direction to a size less
than the bare persistence length of the individual strands, it develops zigzag
conformations which are indicated by an oscillatory tangent-tangent correlation
function in the direction of confinement. Increasing the separation of the
confining plates leads to a crossover to the free behaviour, which takes place
at separations close to the bare persistence length. These results are expected
to be relevant for experiments which involve complexation of two or more stiff
or semiflexible polymers.Comment: 20 pages, 11 figures. PRE (in press
Gender-dependent progression of systemic metabolic states in early childhood
Little is known about the human intra-individual metabolic profile changes over an extended period of time. Here, we introduce a novel concept suggesting that children even at a very young age can be categorized in terms of metabolic state as they advance in development. The hidden Markov models were used as a method for discovering the underlying progression in the metabolic state. We applied the methodology to study metabolic trajectories in children between birth and 4 years of age, based on a series of samples selected from a large birth cohort study. We found multiple previously unknown age- and gender-related metabolome changes of potential medical significance. Specifically, we found that the major developmental state differences between girls and boys are attributed to sphingolipids. In addition, we demonstrated the feasibility of state-based alignment of personal metabolic trajectories. We show that children have different development rates at the level of metabolome and thus the state-based approach may be advantageous when applying metabolome profiling in search of markers for subtle (patho)physiological changes
Tension Dynamics and Linear Viscoelastic Behavior of a Single Semiflexible Polymer Chain
We study the dynamical response of a single semiflexible polymer chain based
on the theory developed by Hallatschek et al. for the wormlike-chain model. The
linear viscoelastic response under oscillatory forces acting at the two chain
ends is derived analytically as a function of the oscillation frequency . We
shall show that the real part of the complex compliance in the low frequency
limit is consistent with the static result of Marko and Siggia whereas the
imaginary part exhibits the power-law dependence +1/2. On the other hand, these
compliances decrease as the power law -7/8 for the high frequency limit. These
are different from those of the Rouse dynamics. A scaling argument is developed
to understand these novel results.Comment: 23 pages, 6 figure
Vibrations of a chain of Xe atoms in a groove of carbon nanotube bundle
We present a lattice dynamics study of the vibrations of a linear chain of Xe
adsorbates in groove positions of a bundle of carbon nanotubes. The
characteristic phonon frequencies are calculated and the adsorbate polarization
vectors discussed. Comparison of the present results with the ones previously
published shows that the adsorbate vibrations cannot be treated as completely
decoupled from the vibrations of carbon nanotubes and that a significant
hybridization between the adsorbate and the tube modes occurs for phonons of
large wavelengths.Comment: 3 PS figure
Survival of women previously diagnosed of melanoma with subsequent pregnancy: a systematic review and meta-analysis and a single-center experience
Review[Abstract] Melanoma incidence has increased over the last few decades. How the prognosis of a previously diagnosed melanoma may be affected by a woman's subsequent pregnancy has been debated in the literature since the 1950s, and the outcomes are essential to women who are melanoma survivors in their childbearing years. The main objective of this systematic review is to improve the understanding of whether the course of melanoma in a woman may be altered by a subsequent pregnancy and to help clinicians' diagnosis. Eligible studies for the systematic review were clinical trials, observational cohort studies and case-control studies that compared prognosis outcomes for non-pregnant patients with melanoma, or pregnant before melanoma diagnosis, versus pregnant patients after a diagnosis of melanoma. The search strategy yielded 1101 articles, of which 4 met the inclusion criteria for the systematic review. All the studies were retrospective non-randomised cohorts with patients with melanomas diagnosed before pregnancy. According to our findings, a subsequent pregnancy was not a significant influence on the outcome of a previous melanoma. However, given the small number of identified studies and the heterogeneous data included, it is recommended to approach these patients with caution, and counselling should be given by known prognostic factors. We also reviewed the medical records of 84 patients of childbearing age (35.8 Âą 6.3 years, range 21-45 years) who were diagnosed with cutaneous invasive melanoma in our hospital between 2008 and 2018 (N = 724). Of these, 11 (13.1%) had a pregnancy after melanoma diagnosis (age at pregnancy: 35.6 Âą 6.3 years). No statistical differences in outcome were detected
Binding of molecules to DNA and other semiflexible polymers
A theory is presented for the binding of small molecules such as surfactants
to semiflexible polymers. The persistence length is assumed to be large
compared to the monomer size but much smaller than the total chain length. Such
polymers (e.g. DNA) represent an intermediate case between flexible polymers
and stiff, rod-like ones, whose association with small molecules was previously
studied. The chains are not flexible enough to actively participate in the
self-assembly, yet their fluctuations induce long-range attractive interactions
between bound molecules. In cases where the binding significantly affects the
local chain stiffness, those interactions lead to a very sharp, cooperative
association. This scenario is of relevance to the association of DNA with
surfactants and compact proteins such as RecA. External tension exerted on the
chain is found to significantly modify the binding by suppressing the
fluctuation-induced interaction.Comment: 15 pages, 7 figures, RevTex, the published versio
A Field-Scale Decision Support System for Assessment and Management of Soil Functions
peer-reviewedAgricultural decision support systems (DSSs) are mostly focused on increasing the supply of individual soil functions such as, e.g., primary productivity or nutrient cycling, while neglecting other important soil functions, such as, e.g., water purification and regulation, climate regulation and carbon sequestration, soil biodiversity, and habitat provision. Making right management decisions for long-term sustainability is therefore challenging, and farmers and farm advisors would greatly benefit from an evidence-based DSS targeted for assessing and improving the supply of several soil functions simultaneously. To address this need, we designed the Soil Navigator DSS by applying a qualitative approach to multi-criteria decision modeling using Decision Expert (DEX) integrative methodology. Multi-criteria decision models for the five main soil functions were developed, calibrated, and validated using knowledge of involved domain experts and knowledge extracted from existing datasets by data mining. Subsequently, the five DEX models were integrated into a DSS to assess the soil functions simultaneously and to provide management advices for improving the performance of prioritized soil functions. To enable communication between the users and the DSS, we developed a user-friendly computer-based graphical user interface, which enables users to provide the required data regarding their field to the DSS and to get textual and graphical results about the performance of each of the five soil functions in a qualitative way. The final output from the DSS is a list of soil mitigation measures that the end-users could easily apply in the field in order to achieve the desired soil function performance. The Soil Navigator DSS has a great potential to complement the Farm Sustainability Tools for Nutrients included in the Common Agricultural Policy 2021â2027 proposal adopted by the European Commission. The Soil Navigator has also a potential to be spatially upgraded to assist decisions on which soil functions to prioritize in a specific region or member state. Furthermore, the Soil Navigator DSS could be used as an educational tool for farmers, farm advisors, and students, and its potential should be further exploited for the benefit of farmers and the society as a whole
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