351 research outputs found
First record of the invasive species Parasaissetia nigra in Greece
Στην παρούσα εργασία γίνεται η πρώτη καταγραφή του είδους Parasaissetia nigra (Nietner) (Hemiptera: Coccidae) επί της ροδιάς στην Ελλάδα. Η παρουσία του είδους αυτού διαπιστώθηκε σε καλλωπιστική ροδιά, τον Ιούνιο του 2014, εντός της Πανεπιστημιούπολης του Γεωπονικού Πανεπιστημίου Αθηνών. Δίδονται πληροφορίες σχετικά με τα μορφολογικά και βιολογικά χαρακτηριστικά, όπως και για την εξάπλωση του εντόμου.In June 2014, the nigra scale Parasaissetia nigra (Nietner) (Hemiptera: Coccidae) was recorded for the first time in Greece on pomegranate, Punica granatum. Its occurrence was observed in an ornamental pomegranate tree in the campus of the Agricultural University of Athens. Information on its morphology, biology and distribution is presented
Approximate encoding of quantum states using shallow circuits
A common requirement of quantum simulations and algorithms is the preparation
of complex states through sequences of 2-qubit gates. For a generic quantum
state, the number of gates grows exponentially with the number of qubits,
becoming unfeasible on near-term quantum devices. Here, we aim at creating an
approximate encoding of the target state using a limited number of gates. As a
first step, we consider a quantum state that is efficiently represented
classically, such as a one-dimensional matrix product state. Using tensor
network techniques, we develop an optimization algorithm that approaches the
optimal implementation for a fixed number of gates. Our algorithm runs
efficiently on classical computers and requires a polynomial number of
iterations only. We demonstrate the feasibility of our approach by comparing
optimal and suboptimal circuits on real devices. We, next, consider the
implementation of the proposed optimization algorithm directly on a quantum
computer and overcome inherent barren plateaus by employing a local cost
function rather than a global one. By simulating realistic shot noise, we
verify that the number of required measurements scales polynomially with the
number of qubits. Our work offers a universal method to prepare target states
using local gates and represents a significant improvement over known
strategies.Comment: 9 + 6 page
An autoparasitoid wasp, inferior at resource exploitation, outcompetes primary parasitoids by using competitor females to produce males
1. Autoparasitoids are intraguild consumers that attack and kill heterospecific
and conspecific parasitoids as well as immature stages of hemipteran hosts, such
as aphids, whiteflies and soft scales. Field experiments assessing the importance of
interspecific competition between autoparasitoids and primary parasitoids, as well as
its impact on herbivore suppression, are scarcely found in the ecological literature.
2. Using field data from 40 olive orchards, this study examined the mechanisms that
regulate: (i) the interspecific competition between primary parasitoids of the genus
Metaphycus and the autoparasitoid Coccophagus lycimnia; and (ii) the density of their
shared herbivore host, the soft scale Saissetia oleae.
3. Metaphycus parasitoids used smaller hosts than C. lycimnia, yet did not outcompete
C. lycimnia. On the other hand, C. lycimnia preferred to use Metaphycus females as
secondary hosts for producing males rather than their own females. This preference
might explain why the autoparasitoid negatively affected the density of the primary
parasitoids.
4. Parasitism by the autoparasitoid C. lycimnia at the beginning of the season was
the sole variable positively related to host mortality throughout the season, showing its
greater effect on herbivore suppression.
5. In this study, an autoparasitoid, inferior at resource exploitation, was shown to
outcompete a primary parasitoid without disrupting herbivore suppression.info:eu-repo/semantics/publishedVersio
The area of horizons and the trapped region
This paper considers some fundamental questions concerning marginally trapped
surfaces, or apparent horizons, in Cauchy data sets for the Einstein equation.
An area estimate for outermost marginally trapped surfaces is proved. The proof
makes use of an existence result for marginal surfaces, in the presence of
barriers, curvature estimates, together with a novel surgery construction for
marginal surfaces. These results are applied to characterize the boundary of
the trapped region.Comment: 44 pages, v3: small changes in presentatio
Unconstrained mining of transcript data reveals increased alternative splicing complexity in the human transcriptome
Mining massive amounts of transcript data for alternative splicing information is paramount to help understand how the maturation of RNA regulates gene expression. We developed an algorithm to cluster transcript data to annotated genes to detect unannotated splice variants. A higher number of alternatively spliced genes and isoforms were found compared to other alternative splicing databases. Comparison of human and mouse data revealed a marked increase, in human, of splice variants incorporating novel exons and retained introns. Previously unannotated exons were validated by tiling array expression data and shown to correspond preferentially to novel first exons. Retained introns were validated by tiling array and deep sequencing data. The majority of retained introns were shorter than 500 nt and had weak polypyrimidine tracts. A subset of retained introns matching small RNAs and displaying a high GC content suggests a possible coordination between splicing regulation and production of noncoding RNAs. Conservation of unannotated exons and retained introns was higher in horse, dog and cow than in rodents, and 64% of exon sequences were only found in primates. This analysis highlights previously bypassed alternative splice variants, which may be crucial to deciphering more complex pathways of gene regulation in human.info:eu-repo/semantics/publishedVersio
Generalized inverse mean curvature flows in spacetime
Motivated by the conjectured Penrose inequality and by the work of Hawking,
Geroch, Huisken and Ilmanen in the null and the Riemannian case, we examine
necessary conditions on flows of two-surfaces in spacetime under which the
Hawking quasilocal mass is monotone. We focus on a subclass of such flows which
we call uniformly expanding, which can be considered for null as well as for
spacelike directions. In the null case, local existence of the flow is
guaranteed. In the spacelike case, the uniformly expanding condition leaves a
1-parameter freedom, but for the whole family, the embedding functions satisfy
a forward-backward parabolic system for which local existence does not hold in
general. Nevertheless, we have obtained a generalization of the weak
(distributional) formulation of this class of flows, generalizing the
corresponding step of Huisken and Ilmanen's proof of the Riemannian Penrose
inequality.Comment: 21 pages, 1 figur
Apparent wave function collapse caused by scattering
Some experimental implications of the recent progress on wave function
collapse are calculated. Exact results are derived for the center-of-mass wave
function collapse caused by random scatterings and applied to a range of
specific examples. The results show that recently proposed experiments to
measure the GRW effect are likely to fail, since the effect of naturally
occurring scatterings is of the same form as the GRW effect but generally much
stronger. The same goes for attempts to measure the collapse caused by quantum
gravity as suggested by Hawking and others. The results also indicate that
macroscopic systems tend to be found in states with (Delta-x)(Delta-p) =
hbar/sqrt(2), but microscopic systems in highly tiltedly squeezed states with
(Delta-x)(Delta-p) >> hbar.Comment: Final published version. 20 pages, Plain TeX, no figures. Online at
http://astro.berkeley.edu/~max/collapse.html (faster from the US), from
http://www.mpa-garching.mpg.de/~max/collapse.html (faster from Europe) or
from [email protected]
Human plasma and serum extracellular small RNA reference profiles and their clinical utility
Circulating extracellular RNAs (exRNAs) have the potential to serve as biomarkers for a wide range of medical conditions. However, limitations in existing exRNA isolation methods and a lack of knowledge on parameters affecting exRNA variability in human samples may hinder their successful discovery and clinical implementation. Using combinations of denaturants, reducing agents, proteolysis, and revised organic extraction, we developed an automated, high-throughput approach for recovery of exRNAs and exDNA from the same biofluid sample. We applied this method to characterize exRNAs from 312 plasma and serum samples collected from 13 healthy volunteers at 12 time points over a 2-month period. Small RNA cDNA library sequencing identified nearly twofold increased epithelial-, muscle-, and neuroendocrine-cell–specific miRNAs in females, while fasting and hormonal cycle showed little effect. External standardization helped to detect quantitative differences in erythrocyte and platelet-specific miRNA contributions and in miRNA concentrations between biofluids. It also helped to identify a study participant with a unique exRNA phenotype featuring a miRNA signature of up to 20-fold elevated endocrine-cell–specific miRNAs and twofold elevated total miRNA concentrations stable for over 1 year. Collectively, these results demonstrate an efficient and quantitative method to discern exRNA phenotypes and suggest that plasma and serum RNA profiles are stable over months and can be routinely monitored in long-term clinical studies
Does the universe in fact contain almost no information?
At first sight, an accurate description of the state of the universe appears
to require a mind-bogglingly large and perhaps even infinite amount of
information, even if we restrict our attention to a small subsystem such as a
rabbit. In this paper, it is suggested that most of this information is merely
apparent, as seen from our subjective viewpoints, and that the algorithmic
information content of the universe as a whole is close to zero. It is argued
that if the Schr\"odinger equation is universally valid, then decoherence
together with the standard chaotic behavior of certain non-linear systems will
make the universe appear extremely complex to any self-aware subsets that
happen to inhabit it now, even if it was in a quite simple state shortly after
the big bang. For instance, gravitational instability would amplify the
microscopic primordial density fluctuations that are required by the Heisenberg
uncertainty principle into quite macroscopic inhomogeneities, forcing the
current wavefunction of the universe to contain such Byzantine superpositions
as our planet being in many macroscopically different places at once. Since
decoherence bars us from experiencing more than one macroscopic reality, we
would see seemingly complex constellations of stars etc, even if the initial
wavefunction of the universe was perfectly homogeneous and isotropic.Comment: 17 pages, LATeX, no figures. Online with refs at
http://astro.berkeley.edu/~max/nihilo.html (faster from the US), from
http://www.mpa-garching.mpg.de/~max/nihilo.html (faster from Europe) or from
[email protected]
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