222 research outputs found
Theory of spin wave excitations of metallic A-type antiferromagnetic manganites
The spin dynamic of the metallic A-type antiferromagnetic manganites is
studied. An effective nearest-neighbour Heisenberg spin wave dispersion is
derived from the double exchange model taking into account the superexchange
interaction between the core spins. The result of inelastic neutron scattering
experiment on is qualitatively reproduced.
Comparing theory with experimental data two main parameters of the model:
nearest-neighbour electron transfer amplitude and superexchange coupling
between the core spins are estimated.Comment: to appear in Phys. Rev.
Stellar archeology: a cosmological view of dwarf galaxies
The origin of dwarf spheroidal galaxies (dSphs) is investigated in a global
cosmological context by simultaneously following the evolution of the Milky Way
Galaxy and its dwarf satellites. This approach enable to study the formation of
dSphs in their proper birth environment and to reconstruct their own merging
histories. The proposed picture simultaneously accounts for several dSph and
Milky Way properties, including the Metallicity Distribution Functions of
metal-poor stars. The observed features are interpreted in terms of physical
processes acting at high redshifts.Comment: 8 pages, 5 figures; "Dwarf Galaxies: Keys to Galaxy Formation and
Evolution" JENAM 2010 Symposium S
Success or failure of primary second/foreign language programmes in Asia: What do the data tell us?
Primary school second/foreign language (SL/FL) programmes in Asia, as well as in other parts of the world, are becoming more common, with many targeting English as the SL or FL. The pressures for such English language programmes come from top-down notions that in a globalised world English is required for societies to be competitive, especially with Asian neighbours, and bottom-up pressures from parents who see English as the key to educational success for their children. In many polities, these forces have resulted in support for policies that introduce early primary school English teaching curricula for all students and have led to parents spending large sums of money on private tutoring or out-of-school tuition. This study reviews the results of nine language planning studies from the Asian region that set out to examine questions such as 'Is this trend towards early primary SL or FL education (mainly English) realistic or is it unattainable and a waste of resources? Do children really benefit from these programmes? What needs to be done to foster learners' success?' These issues are viewed from a language planning and policy perspective through an examination of the language-in-education policy types required for the development of successful programmes. The policies of a number of Asian countries are used as case studies to illustrate this issue
(Photo-)crosslinkable gelatin derivatives for biofabrication applications
Over the recent decades gelatin has proven to be very suitable as an extracellular matrix mimic for bio-fabrication and tissue engineering applications. However, gelatin is prone to dissolution at typical cell culture conditions and is therefore often chemically modified to introduce (photo-)crosslinkable functionalities. These modifications allow to tune the material properties of gelatin, making it suitable for a wide range of biofabrication techniques both as a bioink and as a biomaterial ink (component). The present review provides a non-exhaustive overview of the different reported gelatin modification strategies to yield crosslinkable materials that can be used to form hydrogels suitable for biofabrication applications. The different crosslinking chemistries are discussed and classified according to their mechanism including chain-growth and step-growth polymerization. The step-growth polymerization mechanisms are further classified based on the specific chemistry including different (photo-)click chemistries and reversible systems. The benefits and drawbacks of each chemistry are also briefly discussed. Furthermore, focus is placed on different biofabrication strategies using either inkjet, deposition or light-based additive manufacturing techniques, and the applications of the obtained 3D constructs
Fraction of decays in prompt production measured in pPb collisions at TeV
The fraction of and decays in the prompt
yield, , is measured by
the LHCb detector in pPb collisions at TeV. The study
covers the forward () and backward () rapidity
regions, where is the rapidity in the nucleon-nucleon
center-of-mass system. Forward and backward rapidity samples correspond to
integrated luminosities of 13.6 0.3 nb and 20.8 0.5
nb, respectively. The result is presented as a function of the
transverse momentum in the range 1 GeV/.
The fraction at forward rapidity is compatible with the LHCb
measurement performed in collisions at TeV, whereas the
result at backward rapidity is 2.4 larger than in the forward region
for GeV/. The increase of at low at backward rapidity is compatible with the suppression of the
(2S) contribution to the prompt yield. The lack of in-medium
dissociation of states observed in this study sets an upper limit of
180 MeV on the free energy available in these pPb collisions to dissociate or
inhibit charmonium state formation.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-028.html (LHCb
public pages
Observation of the decays
This paper reports the observation of the decays using proton-proton collision data collected by the
LHCb experiment, corresponding to an integrated luminosity of
. The branching fractions of these decays are measured
relative to the normalisation channel .
The meson is reconstructed in the
decay channel and the products of branching
fractions are measured to be The first uncertainty is
statistical, the second systematic, and the third arises from the uncertainty
of the branching fraction of the
normalisation channel. The last uncertainty in the result is due to
the limited knowledge of the fragmentation fraction ratio, . The
significance for the and signals is larger than
. The ratio of the helicity amplitudes which governs the angular
distribution of the decay
is determined from the data. The ratio of the - and -wave amplitudes is
found to be and its phase rad,
where the first uncertainty is statistical and the second systematic.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-014.html (LHCb
public pages
Search for violation in the phase space of decays with the energy test
A search for violation in and decays is reported.
The search is performed using an unbinned model-independent method known as the
energy test that probes local violation in the phase space of the
decays. The data analysed correspond to an integrated luminosity of
fb collected in proton-proton collisions by the LHCb experiment at
a centre-of-mass energy of ~TeV, amounting to approximately 950000
and 620000 signal candidates for the and modes, respectively. The
method is validated using
and decays, where
-violating effects are expected to be negligible, and using
background-enhanced regions of the signal decays. The results are consistent
with symmetry in both the and the decays, with
-values for the hypothesis of no violation of 70% and 66%,
respectively.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-019.html (LHCb
public pages
Helium identification with LHCb
The identification of helium nuclei at LHCb is achieved using a method based
on measurements of ionisation losses in the silicon sensors and timing
measurements in the Outer Tracker drift tubes. The background from photon
conversions is reduced using the RICH detectors and an isolation requirement.
The method is developed using collision data at
recorded by the LHCb experiment in the years 2016 to 2018, corresponding to an
integrated luminosity of . A total of around helium
and antihelium candidates are identified with negligible background
contamination. The helium identification efficiency is estimated to be
approximately with a corresponding background rejection rate of up to
. These results demonstrate the feasibility of a rich
programme of measurements of QCD and astrophysics interest involving light
nuclei.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-DP-2023-002.html (LHCb public
pages
Electrocatalytic activity of Au nanoparticles onto TiO2 nanotubular layers in oxygen electroreduction reaction: size and support effects
Electrocatalytic activity of both bare high-ordered TiO2 nanotubes (TNTs) and gold nanoparticles (Au NPs) loaded TNTs toward oxygen reduction reaction (ORR) has been examined by cyclic voltammetry (CV). Cyclic voltammograms for Au NPs-TNT electrodes are characterized by an additional wave observed at less negative potentials which is responsible for oxygen electroreduction on the surface of gold NPs. The overpotential for O-2 reduction on the Au surface grows with increasing the temperature of TNT annealing and the Au NPs size. The nature of the effects observed was explained by peculiarities of the electron transport through Schottky barrier formed at the Au NPs - TiO2 interface. The width of the Schottky barrier, determined by semiconductor doping level and Au NPs size, plays a key role in the mechanism of electron transport through the space charge region. (C) 2016 Elsevier Ltd. All rights reserved
Observation of the decays B0(s) â Ds1(2536)âK±
This paper reports the observation of the decays B0
(s) â Ds1(2536)âK± using
proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fbâ1
. The branching fractions of these decays are measured relative
to the normalisation channel B0 â D
0K+Kâ. The Ds1(2536)â meson is reconstructed
in the D
â
(2007)0Kâ decay channel and the products of branching fractions are measured
to be
B(B
0
s â Ds1(2536)âK±) Ă B(Ds1(2536)ââ D
â
(2007)0Kâ)
= (2.49 ± 0.11 ± 0.12 ± 0.25 ± 0.06) Ă 10â5
,
B(B
0â Ds1(2536)âK±) Ă B(Ds1(2536)ââ D
â
(2007)0Kâ)
= (0.510 ± 0.021 ± 0.036 ± 0.050) Ă 10â5
.
The frst uncertainty is statistical, the second systematic, and the third arises from the
uncertainty of the branching fraction of the B0 â D
0K+Kâ normalisation channel.
The last uncertainty in the B0
s
result is due to the limited knowledge of the fragmentation fraction ratio, fs/fd. The signifcance for the B0
s and B0
signals is larger than
10 Ï. The ratio of the helicity amplitudes which governs the angular distribution of the
Ds1(2536)â â D
â
(2007)0Kâ decay is determined from the data. The ratio of the S- and
D-wave amplitudes is found to be 1.11±0.15±0.06 and the phase diference between them
0.70 ± 0.09 ± 0.04 rad, where the frst uncertainty is statistical and the second systematic
- âŠ