228 research outputs found
Ag-Cu alloy surfaces in an oxidizing environment: a first-principles study
Recent experiments on model catalysts have shown that Ag-Cu alloys have
improved selectivity with respect to pure silver for ethylene epoxidation. In
this paper we review our first-principles investigations on the (111) surface
of this alloy and present new findings on other low index surfaces. We find
that, for every surface orientation, the presence of oxygen leads to copper
segregation to the surface. Considering the alloy to be in equilibrium with an
oxygen atmosphere and accounting for the effect of temperature and pressure, we
compute the surface free energy and study the stability of several surface
structures. Investigating the dependence of the surface free energy on the
surface composition, we construct the phase diagram of the alloy for every
surface orientation. Around the temperature, pressure and composition of
interest for practical applications, we find that a limited number of
structures can be present, including a thin layer of copper oxide on top of the
silver surface and copper-free structures. Different surface orientations show
a very similar behavior and in particular a single layer with CuO
stoichiometry, significantly distorted when compared to a layer of bulk CuO,
has a wide range of stability for all orientations. Our results are consistent
with, and help explain, recent experimental measurements
Interface between graphene and liquid Cu from molecular dynamics simulations
Controllable synthesis of defect-free graphene is crucial for applications
since the properties of graphene are highly sensitive to any deviations from
the crystalline lattice. We focus here on the emerging use of liquid Cu
catalysts, which has high potential for fast and efficient industrial-scale
production of high-quality graphene. The interface between graphene and liquid
Cu is studied using force field and ab initio molecular dynamics, revealing a
complete or partial embedding of finite-sized flakes. By analyzing flakes of
different sizes we find that the size-dependence of the embedding can be
rationalized based on the energy cost of embedding versus bending the graphene
flake. The embedding itself is driven by the formation of covalent bonds
between the under-coordinated edge C atoms and the liquid Cu surface, which is
accompanied by a significant charge transfer. In contrast, the central flake
atoms are located around or slightly above 3 {\AA} from the liquid Cu surface
and exhibit weak vdW-bonding and much lower charge transfer. The structural and
electronic properties of the embedded state revealed in our work provides the
atomic-scale information needed to develop effective models to explain the
special growth observed in experiments where various interesting phenomena such
as flake self-assembly and rotational alignment, high growth speeds and low
defect densities in the final graphene product have been observed.Comment: This article may be downloaded for personal use only. Any other use
requires prior permission of the author and AIP Publishing. This article
appeared in J. Chem. Phys. 153, 074702 (2020) and may be found at
https://doi.org/10.1063/5.002012
Atrophy patterns in isolated subscapularis lesions
Background!#!While supraspinatus atrophy can be described according to the system of Zanetti or Thomazeau there is still a lack of characterization of isolated subscapularis muscle atrophy. The aim of this study was to describe patterns of muscle atrophy following repair of isolated subscapularis (SSC) tendon.!##!Methods!#!Forty-nine control shoulder MRI scans, without rotator cuff pathology, atrophy or fatty infiltration, were prospectively evaluated and subscapularis diameters as well as cross sectional areas (complete and upper half) were assessed in a standardized oblique sagittal plane. Calculation of the ratio between the upper half of the cross sectional area (CSA) and the total CSA was performed. Eleven MRI scans of patients with subscapularis atrophy following isolated subscapularis tendon tears were analysed and cross sectional area ratio (upper half /total) determined. To guarantee reliable measurement of the CSA and its ratio, bony landmarks were also defined. All parameters were statistically compared for inter-rater reliability, reproducibility and capacity to quantify subscapularis atrophy.!##!Results!#!The mean age in the control group was 49.7 years (± 15.0). The mean cross sectional area (CSA) was 2367.0 mm!##!Conclusion!#!Analysis of typical atrophy patterns of the subscapularis muscle demonstrates that the CSA ratio represents a reliable and reproducible assessment tool in quantifying subscapularis atrophy. We propose the classification of subscapularis atrophy as Stage I (mild atrophy) in case of reduction of the cross sectional area ratio < 0.4, Stage II (moderate atrophy) in case of < 0.35 and Stage III (severe atrophy) if < 0.3
"Wrongful discrimination" - a tautological claim?
Is it tautological to call an action "wrongful discrimination?" Some philosophers and political theorists answer this question in the affirmative and claim that the term "discrimination" is intrinsically evaluative. Others agree that "discrimination" usually conveys the action’s moral wrongness but claim that the term can be used in a purely descriptive way. In this paper, we present two corpus studies and two experiments designed to test whether the folk concept of discrimination is evaluative. We demonstrate that the term has undergone a historical development and is nowadays no longer used purely descriptively. Further, we show that this evaluation cannot be cancelled without yielding a contradiction. We conclude that the descriptive use of "discriminatory" is a thing of the past
Asymptotic safety of gravity and the Higgs boson mass
There are indications that gravity is asymptotically safe. The Standard Model
(SM) plus gravity could be valid up to arbitrarily high energies. Supposing
that this is indeed the case and assuming that there are no intermediate energy
scales between the Fermi and Planck scales we address the question of whether
the mass of the Higgs boson can be predicted. For a positive gravity
induced anomalous dimension the running of the quartic scalar
self interaction at scales beyond the Planck mass is determined by a
fixed point at zero. This results in GeV, with only a few
GeV uncertainty. This prediction is independent of the details of the short
distance running and holds for a wide class of extensions of the SM as well.
For one finds in the interval GeV, now sensitive to and other properties of the
short distance running. The case is favored by explicit
computations existing in the literature.Comment: 8 pages, typos corrected, references added. Journal versio
Top Partner Discovery in the channel at the LHC
In this paper we study the discovery potential of the LHC run II for heavy
vector-like top quarks in the decay channel to a top and a boson. Despite
the usually smaller branching ratio compared to charged-current decays, this
channel is rather clean and allows for a complete mass reconstruction of the
heavy top. The latter is achieved in the leptonic decay channel of the
boson and in the fully hadronic top channel using boosted jet and jet
substructure techniques. To be as model-independent as possible, a simplified
model approach with only two free parameters has been applied. The results are
presented in terms of parameter space regions for evidence or
discovery for such new states in that channel.Comment: 24 pages, 8 figures, version 2 updated to JHEP 01 (2015) 08
Entanglement Entropy dynamics in Heisenberg chains
By means of the time-dependent density matrix renormalization group algorithm
we study the zero-temperature dynamics of the Von Neumann entropy of a block of
spins in a Heisenberg chain after a sudden quench in the anisotropy parameter.
In the absence of any disorder the block entropy increases linearly with time
and then saturates. We analyze the velocity of propagation of the entanglement
as a function of the initial and final anisotropies and compare, wherever
possible, our results with those obtained by means of Conformal Field Theory.
In the disordered case we find a slower (logarithmic) evolution which may
signals the onset of entanglement localization.Comment: 15 pages, 9 figure
Benefits from using mixed precision computations in the ELPA-AEO and ESSEX-II eigensolver projects
We first briefly report on the status and recent achievements of the ELPA-AEO
(Eigenvalue Solvers for Petaflop Applications - Algorithmic Extensions and
Optimizations) and ESSEX II (Equipping Sparse Solvers for Exascale) projects.
In both collaboratory efforts, scientists from the application areas,
mathematicians, and computer scientists work together to develop and make
available efficient highly parallel methods for the solution of eigenvalue
problems. Then we focus on a topic addressed in both projects, the use of mixed
precision computations to enhance efficiency. We give a more detailed
description of our approaches for benefiting from either lower or higher
precision in three selected contexts and of the results thus obtained
Effectiveness and safety of first-generation protease inhibitors in real-world patients with hepatitis C virus genotype 1 infection in Brazil: a multicenter study
OBJECTIVE: To evaluate the effectiveness and safety of first-generation protease inhibitors for the treatment of genotype 1 hepatitis C virus-infected patients at Brazilian reference centers. METHODS: This multicenter cross-sectional study included hepatitis C virus genotype 1 monoinfected patients treated with Peg-interferon, ribavirin, and either boceprevir (n=158) or telaprevir (n=557) between July 2013 and April 2014 at 15 reference centers in Brazil. Demographic, clinical, virological, and adverse events data were collected during treatment and follow-up. RESULTS: Of the 715 patients, 59% had cirrhosis and 67.1% were treatment-experienced. Based on intention-to-treat analysis, the overall sustained viral response was 56.6%, with similar effectiveness in both groups (51.9% for boceprevir and 58% for telaprevir, p=0.190). Serious adverse events occurred in 44.2% of patients, and six deaths (0.8%) were recorded. Cirrhotic patients had lower sustained viral response rates than non-cirrhotic patients (46.9% vs. 70.6%, p 465 years, diagnosis of cirrhosis, and abnormal hemoglobin levels/platelet counts prior to treatment were associated with serious adverse events. CONCLUSION: Although serious adverse events rates were higher in this infected population, sustained viral response rates were similar to those reported for other patient cohorts.Univ Sao Paulo, Fac Med, Dept Molestias Infecciosas & Parasitarias, Sao Paulo, SP, BrazilUniv Fed Rio de Janeiro, Rio De Janeiro, RJ, BrazilCtr Referencia & Treinamento DST Aids, Sao Paulo, SP, BrazilCDH, Rio De Janeiro, RJ, BrazilHosp Fed Servidores Estado Rio de Janeiro HFSE, Setor Gastrohepatol, Rio De Janeiro, RJ, BrazilUniv Sao Paulo, Fac Med, Dept Gastroenterol & Hepatol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo UNIFESP, Disciplina Gastroenterol, EPM, Sao Paulo, SP, BrazilUniv Fed Sao Paulo UNIFESP, EPM, Disciplina Infectol, Sao Paulo, SP, BrazilUniv Sao Paulo, FMRP, Dept Clin Med, Div Gastroenterol, Sao Paulo, SP, Brazil| Univ Fed do Maranhao UFMA, HUPD, Ctr Pesquisa Clin, Sao Luis, MA, BrazilUniv Fed Estado Rio de Janeiro UNIRIO, Disciplina Clin Med & Gastroenterol, Rio De Janeiro, RJ, BrazilUniv Fed Rio do Grande Sul UFRGS, Dept Med Interna, Porto Alegre, RS, BrazilUniv Fed Espirito Santo, Ambulatorio HIV AIDS Hepatites Virais, Vitoria, ES, BrazilSMS, Ctr Orientacao & Aconselhamento, Foz Do Iguacu, PR, BrazilUniv Estado Rio de Janeiro UERJ, Serv Gastroenterol, Rio De Janeiro, RJ, BrazilIMT, Lab Virol LIM 52, Sao Paulo, SP, BrazilUniv Fed Sao Paulo UNIFESP, Disciplina Gastroenterol, EPM, Sao Paulo, SP, BrazilUniv Fed Sao Paulo UNIFESP, EPM, Disciplina Infectol, Sao Paulo, SP, BrazilWeb of Scienc
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