135 research outputs found
Formation of a "Cluster Molecule" (C20)2 and its thermal stability
The possible formation of a "cluster molecule" (C20)2 from two single C20
fullerenes is studied by the tight-binding method. Several (C20)2 isomers in
which C20 fullerenes are bound by strong covalent forces and retain their
identity are found; actually, these C20 fullerenes play the role of "atoms" in
the "cluster molecule". The so-called open-[2+2] isomer has a minimum energy.
Its formation path and thermal stability at T = 2000 - 4000 K are analyzed in
detail. This isomer loses its molecular structure due to either the decay of
one of C20 fullerenes or the coalescence of two C20 fullerenes into a C40
cluster. The energy barriers for the metastable open-[2+2] configuration are
calculated to be U = 2 - 5 eV.Comment: 21 pages, 8 figure
Decay and fusion as two different mechanisms of stability loss for the (C_20)_2 cluster dimer
The thermal stability of the (C_20)_2 cluster dimer consisting of two C_20
fullerenes is examined using a tight-binding approach. Molecular dynamics
simulations of the (C_20)_2 dimer at temperatures T = 2000 - 3500 K show that
the finite lifetime \tau of this metastable system is determined by two
fundamentally different processes, the decay of one of the C_20 fullerenes and
the fusion of two C_20 fullerenes into the C_40 cluster. The activation
energies for these processes Ea = 3.4 and 2.7 eV, respectively, as well as
their frequency factors, have been determined by analyzing the dependence of
\tau on T.Comment: Slightly modified version of the paper to appear in JETP Let
Induction of Ig light chain gene rearrangement in heavy chain-deficient B cells by activated Ras
Improved Bootstrapping for Approximate Homomorphic Encryption
Since Cheon et al. introduced a homomorphic encryption
scheme for approximate arithmetic (Asiacrypt â17), it has been recognized
as suitable for important real-life usecases of homomorphic encryption,
including training of machine learning models over encrypted
data. A follow up work by Cheon et al. (Eurocrypt â18) described an
approximate bootstrapping procedure for the scheme. In this work, we
improve upon the previous bootstrapping result. We improve the amortized
bootstrapping time per plaintext slot by two orders of magnitude,
from ∼ 1 second to ∼ 0.01 second. To achieve this result, we adopt
a smart level-collapsing technique for evaluating DFT-like linear transforms
on a ciphertext. Also, we replace the Taylor approximation of the
sine function with a more accurate and numerically stable Chebyshev approximation,
and design a modified version of the Paterson-Stockmeyer
algorithm for fast evaluation of Chebyshev polynomials over encrypted
data
Self-Assembled Poly(4-vinylpyridine)âSurfactant Systems Using Alkyl and Alkoxy Phenylazophenols
Metabolic engineering of Rhizopus oryzae for the production of platform chemicals
Rhizopus oryzae is a filamentous fungus belonging to the Zygomycetes. It is among others known for its ability to produce the sustainable platform chemicals l-(+)-lactic acid, fumaric acid, and ethanol. During glycolysis, all fermentable carbon sources are metabolized to pyruvate and subsequently distributed over the pathways leading to the formation of these products. These platform chemicals are produced in high yields on a wide range of carbon sources. The yields are in excess of 85Â % of the theoretical yield for l-(+)-lactic acid and ethanol and over 65Â % for fumaric acid. The study and optimization of the metabolic pathways involved in the production of these compounds requires well-developed metabolic engineering tools and knowledge of the genetic makeup of this organism. This review focuses on the current metabolic engineering techniques available for R. oryzae and their application on the metabolic pathways of the main fermentation products
Basic Communicative Activities in Coaching: A Linguistic Contribution to the Coaching Process Research
El campo de las ciencias y la educaciĂłn superior entre el monopolio del inglĂ©s y el plurilingĂŒismo: elementos para una polĂtica del lenguaje en AmĂ©rica Latina
Event-by-Event Analysis of Collision-Induced Cluster-Ion Fragmentation: Sequential Monomer Evaporation versus Fission Reactions
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