509 research outputs found
Deglaciation constraints in the Parâng Mountains, Southern Romania, using surface exposure dating
Cosmogenic nuclide surface exposure ages have been widely used to constrain glacial chronologies in the European regions. This paper brings new evidence that the Romanian Carpathians sheltered mountain glaciers in their upper valleys and cirques until the end of the last glaciation. Twenty-four 10Be surface exposure ages were obtained from boulders on moraine crests in the central area of the Parâng Mountains, Southern Carpathians. Exposure ages were used to constrain the timing of the deglaciation events during the Late Glacial. The lowest boulders yielded an age of 13.0 ± 1.1 (1766 m) and final deglaciation occurred at 10.2 ± 0.9 ka (2055 m). Timing of the Late Glacial events and complete deglaciation reported in this study are consistent with, and confirm, previously reported ages of deglaciation within the Carpathian and surrounding European region
Addendum to "Nonlinear quantum evolution with maximal entropy production"
The author calls attention to previous work with related results, which has
escaped scrutiny before the publication of the article "Nonlinear quantum
evolution with maximal entropy production", Phys.Rev.A63, 022105 (2001).Comment: RevTex-latex2e, 2pgs., no figs.; brief report to appear in the May
2001 issue of Phys.Rev.
Local cloning of entangled states
We investigate the conditions under which a set \SC of pure bipartite
quantum states on a system can be locally cloned deterministically
by separable operations, when at least one of the states is full Schmidt rank.
We allow for the possibility of cloning using a resource state that is less
than maximally entangled. Our results include that: (i) all states in \SC
must be full Schmidt rank and equally entangled under the -concurrence
measure, and (ii) the set \SC can be extended to a larger clonable set
generated by a finite group of order , the number of states in the
larger set. It is then shown that any local cloning apparatus is capable of
cloning a number of states that divides exactly. We provide a complete
solution for two central problems in local cloning, giving necessary and
sufficient conditions for (i) when a set of maximally entangled states can be
locally cloned, valid for all ; and (ii) local cloning of entangled qubit
states with non-vanishing entanglement. In both of these cases, a maximally
entangled resource is necessary and sufficient, and the states must be related
to each other by local unitary "shift" operations. These shifts are determined
by the group structure, so need not be simple cyclic permutations. Assuming
this shifted form and partially entangled states, then in D=3 we show that a
maximally entangled resource is again necessary and sufficient, while for
higher dimensional systems, we find that the resource state must be strictly
more entangled than the states in \SC. All of our necessary conditions for
separable operations are also necessary conditions for LOCC, since the latter
is a proper subset of the former. In fact, all our results hold for LOCC, as
our sufficient conditions are demonstrated for LOCC, directly.Comment: REVTEX 15 pages, 1 figure, minor modifications. Same as the published
version. Any comments are welcome
THE CURRENT STATE OF THE VITIVINICULTURE SECTOR IN ROMANIA
After Romania accessed the European Union in 2007 and especially after 2009, there were major changes in Romania in the viticulture and winemaking field regarding the alignment of the legal framework to the Common Agricultural Policy (P.A.C.). During the post-accession, there were both important quality leaps in this field and a series of difficulties imposing a synthetic analysis in order to identify certain solutions to diversify the vineyard range and to improve the quality of the winemaking products.In this framework, concerning the strategies and policies implemented in the vitiviniculture sector in Romania during the last decade, this study refers to the following aspects: assessing the reconversion-restructuring stage of the vineyards in Romania, assessing the stage of implementing national strategies to produce high-quality wine (with PDO and PGI), as important premises for providing quality and specificity to the wine products
THERMAL REGIME DURING COLD ACCLIMATION AND DORMANT SEASON OF GRAPEVINES IN CONTEXT OF CLIMATE CHANGES- HILLS OF CRAIOVA VINEYARD (ROMANIA)
The thermal regime during the autumn-winter seasons plays a decisive role in cold acclimation and survival grapevine in cold climates. This study aims at assessing the time variability of the thermal regime during dormant season, between 1961-2021, in the Hills of Craiova vineyard and its potential implications on the grapevine, especially regarding its acclimation to cold and its vulnerability to frost. The following observations and analytical data were used in order to assess parameters and indicators with negative thermal stress potential: minimum and maximum temperature (daily, monthly averages), absolute maximum and minimum monthly temperatures, the duration of frost (days), the frequency of several low-temperature thresholds and the temperatures preceding frost episodes. Â
Information theoretic treatment of tripartite systems and quantum channels
A Holevo measure is used to discuss how much information about a given POVM
on system is present in another system , and how this influences the
presence or absence of information about a different POVM on in a third
system . The main goal is to extend information theorems for mutually
unbiased bases or general bases to arbitrary POVMs, and especially to
generalize "all-or-nothing" theorems about information located in tripartite
systems to the case of \emph{partial information}, in the form of quantitative
inequalities. Some of the inequalities can be viewed as entropic uncertainty
relations that apply in the presence of quantum side information, as in recent
work by Berta et al. [Nature Physics 6, 659 (2010)]. All of the results also
apply to quantum channels: e.g., if \EC accurately transmits certain POVMs,
the complementary channel \FC will necessarily be noisy for certain other
POVMs. While the inequalities are valid for mixed states of tripartite systems,
restricting to pure states leads to the basis-invariance of the difference
between the information about contained in and .Comment: 21 pages. An earlier version of this paper attempted to prove our
main uncertainty relation, Theorem 5, using the achievability of the Holevo
quantity in a coding task, an approach that ultimately failed because it did
not account for locking of classical correlations, e.g. see [DiVincenzo et
al. PRL. 92, 067902 (2004)]. In the latest version, we use a very different
approach to prove Theorem
Quantum Error Correcting Codes Using Qudit Graph States
Graph states are generalized from qubits to collections of qudits of
arbitrary dimension , and simple graphical methods are used to construct
both additive and nonadditive quantum error correcting codes. Codes of distance
2 saturating the quantum Singleton bound for arbitrarily large and are
constructed using simple graphs, except when is odd and is even.
Computer searches have produced a number of codes with distances 3 and 4, some
previously known and some new. The concept of a stabilizer is extended to
general , and shown to provide a dual representation of an additive graph
code.Comment: Version 4 is almost exactly the same as the published version in
Phys. Rev.
Multipartite Entanglement Evolution Under Separable Operations
We study how multi-partite entanglement evolves under the paradigm of
separable operations, which include the local operations and classical
communication (LOCC) as a special case. We prove that the average "decay" of
entanglement induced by a separable operation is measure independent (among
SL-invariant ones) and state independent: the ratio between the average output
entanglement and the initial entanglement is solely a function of the separable
operation, regardless of the input state and of the SL-invariant entanglement
measure being used. We discuss the "disentangling power" of a quantum channel
and show that it exhibits a similar state invariance as the average
entanglement decay ratio. Our Rapid Communication significantly extends the
bipartite results of Ref. [1-3] as well as the multi-partite one of Ref. [4],
all of the previous work being restricted to one-sided or particular noise
models.Comment: Replaced by the published version, comments are welcome
Support effects in a Rh diamine complex heterogenized on carbon materials
The Rh diamine complex [Rh(COD)NH2(CH2)2NH(CH2)3Si(OCH3)3] BF4 was heterogenized by covalent bonding on two carbon xerogels and on carbon nanofibers, with the objective of preparing hydrogenation hybrid catalysts. Gas adsorption, SEM, TEM, DTP, ICP-OES and XPS were used for characterization. The results indicate that the active molecule is mainly located in supermicropores and produces microporosity blockage. The hybrid catalysts are more active than the homogeneous complex, but the Rh complex is partially reduced upon reaction. This modification is related to the nature of the support, which also shows effects in the stabilization against sintering of the Rh particles formed. The support porosity is a key factor in the selectivity differences between the catalysts.The authors thank the financial support to MICINN, Project MAT2009-07150, to GVA and FEDER, Project Prometeo 2009/047, and to MEC for the FPU scholarship of C.C.G
Non-covalent immobilization of RhDuphos on carbon nanotubes and carbon xerogels
The immobilization of the chiral complex RhDuphos, by electrostatic or π–π (adsorption) interactions, on carbon nanotubes and carbon xerogels is investigated. To promote such interactions, the supports were either oxidized or heat treated to create carboxylic type surface groups or an apolar surface, respectively. The catalysts were tested in the hydrogenation of methyl 2-acetamidoacrylate. The prepared hybrid catalysts are less active than the homogeneous RhDuphos, but most of them show a high enantioselectivity and the one prepared with the oxidized carbon xerogel is also reusable, being able to give a high substrate conversion, keeping as well a high enantioselectivity. The anchorage by electrostatic interactions is more interesting than the anchorage by π–π interactions, as the π–π adsorption method produces a modification of the metal complex structure leading to an active hybrid catalyst but without enantioselectivity. The creation of carboxylic groups on the support surface has led to some hindering of the complex leaching.The authors thank the financial support to MINECO, Project MAT2012-32832, to GVA and FEDER, Project PROMETEO 2009/047, and to MEC for the FPU scholarship of C.C.G
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