158 research outputs found
Directed percolation effects emerging from superadditivity of quantum networks
Entanglement indcued non--additivity of classical communication capacity in
networks consisting of quantum channels is considered. Communication lattices
consisiting of butterfly-type entanglement breaking channels augmented, with
some probability, by identity channels are analyzed. The capacity
superadditivity in the network is manifested in directed correlated bond
percolation which we consider in two flavours: simply directed and randomly
oriented. The obtained percolation properties show that high capacity
information transfer sets in much faster in the regime of superadditive
communication capacity than otherwise possible. As a byproduct, this sheds
light on a new type of entanglement based quantum capacity percolation
phenomenon.Comment: 6 pages, 4 figure
Influence of Sn and Pb ions substitutions on dielectric properties of barium titanate
The results of the microstructural and dielectric measurements of (Ba1-xPbx)(Ti1-xSnx)O3 (BPTSx) (x = 0, 0.05, 0.10, 0.30) polycrystalline samples are presented. The samples were obtained by means of a high temperature synthesis and their expected stoichiometry was confirmed by energy dispersive spectroscopy (EDS) measurements. The dielectric properties of BPTSx were studied with the use of broadband dielectric spectroscopy. The measurements over a wide range of temperature (from 140 K to 600 K) and frequency (from 0.1 Hz to 10 MHz) were performed. The experimental results indicate an influence of Pb ions in a sublattice A and Sn ions in a sublattice B substitution on paraelectric - ferroelectric phase transition parameters. Diffused phase transitions from a paraelectric to ferroelectric state (for x = 0.10 and x = 0.30) were observed. From the electric modulus measurements in the frequency domain the relaxation times and the activation energy were determined
Structure and magnetic properties of Bi5Ti3FeO15 ceramics prepared by sintering, mechanical activation and EDAMM process. A comparative study
Three different methods were used to obtain Bi5Ti3FeO15 ceramics, i.e. solid-state sintering, mechanical activation (MA) with subsequent thermal treatment, and electrical discharge assisted mechanical milling (EDAMM). The structure and magnetic properties of produced Bi5Ti3FeO15 samples were characterized using X-ray diffraction and Mössbauer spectroscopy. The purest Bi5Ti3FeO15 ceramics was obtained by standard solid-state sintering method. Mechanical milling methods are attractive because the Bi5Ti3FeO15 compound may be formed at lower temperature or without subsequent thermal treatment. In the case of EDAMM process also the time of processing is significantly shorter in comparison with solid-state sintering method. As revealed by Mössbauer spectroscopy, at room temperature the Bi5Ti3FeO15 ceramics produced by various methods is in paramagnetic state
Optimal entanglement witnesses from generalized reduction and Robertson maps
We provide a generalization of the reduction and Robertson positive maps in
matrix algebras. They give rise to a new class of optimal entanglement
witnesses. Their structural physical approximation is analyzed. As a byproduct
we provide a new examples of PPT (Positive Partial Transpose) entangled states.Comment: 14 page
On structural physical approximations and entanglement breaking maps
Very recently a conjecture saying that the so-called structural physical
approximations (SPAa) to optimal positive maps (optimal entanglement witnesses)
give entanglement breaking (EB) maps (separable states) has been posed [J. K.
Korbicz {\it et al.}, Phys. Rev. A {\bf 78}, 062105 (2008)]. The main purpose
of this contribution is to explore this subject. First, we extend the set of
entanglement witnesses (EWs) supporting the conjecture. Then, we ask if SPAs
constructed from other than the depolarizing channel maps also lead to EB maps
and show that in general this is not the case. On the other hand, we prove an
interesting fact that for any positive map there exists an EB channel
such that the SPA of constructed with the aid of is
again an EB channel. Finally, we ask similar questions in the case of
continuous variable systems. We provide a simple way of construction of SPA and
prove that in the case of the transposition map it gives EB channel.Comment: 22 pages, improved version, accepted by Journal of Physics
Subadditivity of the minimum output entropy and superactivation of the classical capacity of quantum multiple access channels
We study subadditivity of the minimum output entropy () of quantum
multiple access channels (MACs). We provide an example of violation of the
additivity theorem for known in classical information theory. Our
result is based on a fundamental property of i.e. independence of each
sender. The channels used in the example can be constructed explicitly. On the
basis of subadditivity of we also provide an example of extremal
superadditivity (super activation) of the classical capacity region of MACs.Comment: 5 pages, 3 figure
Plejotropowe działanie statyn
Statyny, czyli inhibitory reduktazy 3-hydroksy-3-metyloglutarylokoenzymu A, wprowadzono do leczenia jako
leki hipolipemizujące. Od tego momentu poznano wiele działań statyn niezależnych od mechanizmu obniżania
stężenia cholesterolu. Plejotropizm leków z tej grupy przejawia się między innymi działaniem ochronnym
na śródbłonek naczyniowy, stabilizacją blaszki miażdżycowej, efektem przeciwzapalnym oraz wpływem na
układ krzepnięcia i fibrynolizy.
Działanie statyn wykorzystuje się w pierwotnej i wtórnej prewencji choroby wieńcowej, udaru niedokrwiennego,
a także w zapobieganiu powikłaniom naczyniowym u chorych na cukrzycę. W przyszłości, być może, znajdą
zastosowanie w leczeniu chorób autoimmunologicznych, neurodegeneracyjnych czy w transplantologii.
Siła działania statyn zależy od rodzaju preparatu oraz od dawki. Zastosowanie dużych dawek wiąże się
z większą skutecznością, ale także zwiększa ryzyko wystąpienia działań niepożądanych, takich jak zaburzenia
żołądkowo-jelitowe, wzrost stężenia transaminaz, miopatia, a w skrajnych przypadkach nawet rabdomioliza.
Ze względu na wielokierunkowość działań statyny wykazują duży potencjał terapeutyczny. Obecnie są szeroko
stosowane w kardiologii, ale ich przyszłość będzie prawdopodobnie związana również z innymi dziedzinami
medycyny
Can Energetic Terahertz Pulses Initiate Surface Catalytic Reactions on the Picosecond Time Scale?
In preparation for picosecond pump-probe experiments at the SwissFELX-ray laser facility, the feasibility of collectively initiating surface chemical reactions using energetic pulses of terahertz radiation is being tested
The drivers of change for the contribution of small farms to regional food security in Europe
The capacity of the food system to respond to the economic, demographic and environmental challenges ahead has become a topic of increasing interest, with particular attention to the roles and responsibilities of the different actors to ensure more sustainable food systems that can guarantee food and nutrition security for all. In this paper we approach the need to better understand the factors that can condition the potential contribution of small farms to regional food and nutrition security in Europe, acknowledging the role that small farms play in Europe at present. The analysis is based on a survey to 94 experts from 17 regions (NUTS3 level) in 11 different European countries, which identified the drivers of change according to the regional experts. These drivers were then categorized and their relative relevance assessed. The results indicate that some relevant drivers in the European context are linked to the capacity to adopt technologies and practices allowing adaptation to climate change, and the capacity to connect to food markets, with emphasis in the need for cooperation and collective action. The weight of other more European-specific drivers such as ‘consumer values and habits’ reveal that the future role of small farms will be very dependent on a societal change, with equity becoming a relevant component of consumers’ choice
Quantum internet using code division multiple access
A crucial open problem in large-scale quantum networks is how to efficiently
transmit quantum data among many pairs of users via a common data-transmission
medium. We propose a solution by developing a quantum code division multiple
access (q-CDMA) approach in which quantum information is chaotically encoded to
spread its spectral content, and then decoded via chaos synchronization to
separate different sender-receiver pairs. In comparison to other existing
approaches, such as frequency division multiple access (FDMA), the proposed
q-CDMA can greatly increase the information rates per channel used, especially
for very noisy quantum channels.Comment: 29 pages, 6 figure
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