57 research outputs found
α-Latrotoxin receptor Implications in nerve terminal function
Abstractα-Latrotoxin is a potent stimulator of neurotransmitter release from nerve terminals. High affinity membrane α-latrotoxin receptor was purified in an active binding form. It is a membrane glycoprotein (Mr 160,000â220,000) which may be complexed to a smaller polypeptide (Mr 29,000). The structure of the receptor protein suggests that it may be a synapse-specific cell recognition molecule. Intracellularly, the α-latrotoxin receptor interacts with synaptotagmin, a calcium- and phospholipid-binding protein specifically localized in the synaptic vesicle membrane. This interaction may be important for targeting of synaptic vesicles to presynaptic release sites
Benchmarking acid and base dopants with respect to enabling the ice V to XIII and ice VI to XV hydrogen-ordering phase transitions
Doping the hydrogen-disordered phases of ice V, VI and XII with hydrochloric
acid (HCl) has led to the discovery of their hydrogen-ordered counterparts ices
XIII, XV and XIV. Yet, the mechanistic details of the hydrogen-ordering phase
transitions are still not fully understood. This includes in particular the
role of the acid dopant and the defect dynamics that it creates within the
ices. Here we investigate the effects of several acid and base dopants on the
hydrogen ordering of ices V and VI with calorimetry and X-ray diffraction. HCl
is found to be most effective for both phases which is attributed to a
favourable combination of high solubility and strong acid properties which
create mobile H3O+ defects that enable the hydrogen-ordering processes.
Hydrofluoric acid (HF) is the second most effective dopant highlighting that
the acid strengths of HCl and HF are much more similar in ice than they are in
liquid water. Surprisingly, hydrobromic acid doping facilitates hydrogen
ordering in ice VI whereas only a very small effect is observed for ice V.
Conversely, lithium hydroxide (LiOH) doping achieves a performance comparable
to HF-doping in ice V but it is ineffective in the case of ice VI. Sodium
hydroxide, potassium hydroxide (as previously shown) and perchloric acid doping
are ineffective for both phases. These findings highlight the need for future
computational studies but also raise the question why LiOH-doping achieves
hydrogen-ordering of ice V whereas potassium hydroxide doping is most effective
for the 'ordinary' ice Ih.Comment: 18 pages, 7 figures, 1 tabl
Talking quiescence: a rigorous theory that supports parallel composition, action hiding and determinisation
The notion of quiescence - the absence of outputs - is vital in both
behavioural modelling and testing theory. Although the need for quiescence was
already recognised in the 90s, it has only been treated as a second-class
citizen thus far. This paper moves quiescence into the foreground and
introduces the notion of quiescent transition systems (QTSs): an extension of
regular input-output transition systems (IOTSs) in which quiescence is
represented explicitly, via quiescent transitions. Four carefully crafted rules
on the use of quiescent transitions ensure that our QTSs naturally capture
quiescent behaviour.
We present the building blocks for a comprehensive theory on QTSs supporting
parallel composition, action hiding and determinisation. In particular, we
prove that these operations preserve all the aforementioned rules.
Additionally, we provide a way to transform existing IOTSs into QTSs, allowing
even IOTSs as input that already contain some quiescent transitions. As an
important application, we show how our QTS framework simplifies the fundamental
model-based testing theory formalised around ioco.Comment: In Proceedings MBT 2012, arXiv:1202.582
Enhancement of Anisotropy due to Fluctuations in Quasi-One-Dimensional Antiferromagnets
It is shown that the observed anisotropy of magnetization at high magnetic
fields in RbMnBr3 , a quasi-one-dimensional antiferromagnet on a distorted
stacked triangular lattice, is due to quantum and thermal fluctuations. These
fluctuations are taken into account in the framework of linear spin-wave theory
in the region of strong magnetic fields. In this region the divergent
one-dimensional integrals are cut off by magnetic field and the bare easy-plane
anisotropy. Logarithmical dependence on the cutoff leads to the "enhancement"
of the anisotropy in magnetization. Comparison between magnetization data and
our theory with parameters obtained from neutron scattering experiments has
been done.Comment: 15 pages + 5 postscript figures available upon request, RevTex
Towards Symbolic Model-Based Mutation Testing: Combining Reachability and Refinement Checking
Model-based mutation testing uses altered test models to derive test cases
that are able to reveal whether a modelled fault has been implemented. This
requires conformance checking between the original and the mutated model. This
paper presents an approach for symbolic conformance checking of action systems,
which are well-suited to specify reactive systems. We also consider
nondeterminism in our models. Hence, we do not check for equivalence, but for
refinement. We encode the transition relation as well as the conformance
relation as a constraint satisfaction problem and use a constraint solver in
our reachability and refinement checking algorithms. Explicit conformance
checking techniques often face state space explosion. First experimental
evaluations show that our approach has potential to outperform explicit
conformance checkers.Comment: In Proceedings MBT 2012, arXiv:1202.582
Observation of the Cabibbo-suppressed decay Xi_c+ -> p K- pi+
We report the first observation of the Cabibbo-suppressed charm baryon decay
Xi_c+ -> p K- pi+. We observe 150 +- 22 events for the signal. The data were
accumulated using the SELEX spectrometer during the 1996-1997 fixed target run
at Fermilab, chiefly from a 600 GeV/c Sigma- beam. The branching fractions of
the decay relative to the Cabibbo-favored Xi_c+ -> Sigma+ K- pi+ and Xi_c+ ->
X- pi+ pi+ are measured to be B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> Sigma+ K- pi+) =
0.22 +- 0.06 +- 0.03 and B(Xi_c+ -> p K- pi+)/B(Xi_c+ -> X- pi+ pi+) = 0.20 +-
0.04 +- 0.02, respectively.Comment: 5 pages, RevTeX, 3 figures (postscript), Submitted to Phys. Rev. Let
Methane Clumped Isotopes: Progress and Potential for a New Isotopic Tracer
The isotopic composition of methane is of longstanding geochemical interest, with important implications for understanding petroleum systems, atmospheric greenhouse gas concentrations, the global carbon cycle, and life in extreme environments. Recent analytical developments focusing on multiply substituted isotopologues (âclumped isotopesâ) are opening a valuable new window into methane geochemistry. When methane forms in internal isotopic equilibrium, clumped isotopes can provide a direct record of formation temperature, making this property particularly valuable for identifying different methane origins. However, it has also become clear that in certain settings methane clumped isotope measurements record kinetic rather than equilibrium isotope effects. Here we present a substantially expanded dataset of methane clumped isotope analyses, and provide a synthesis of the current interpretive framework for this parameter. In general, clumped isotope measurements indicate plausible formation temperatures for abiotic, thermogenic, and microbial methane in many geological environments, which is encouraging for the further development of this measurement as a geothermometer, and as a tracer for the source of natural gas reservoirs and emissions. We also highlight, however, instances where clumped isotope derived temperatures are higher than expected, and discuss possible factors that could distort equilibrium formation temperature signals. In microbial methane from freshwater ecosystems, in particular, clumped isotope values appear to be controlled by kinetic effects, and may ultimately be useful to study methanogen metabolism
Towards ready-to-use 3-D scaffolds for regenerative medicine: adhesion-based cryopreservation of human mesenchymal stem cells attached and spread within alginateâgelatin cryogel scaffolds
Observation of the Mass Difference Between Neutral Charm-Meson Eigenstates
A measurement of mixing and
C
P
violation in neutral charm mesons is performed using data reconstructed in proton-proton collisions collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of
5.4
â
â
fb
â
1
. A total of 30.6 million
D
0
â
K
0
S
Ï
+
Ï
â
decays are analyzed using a method optimized for the measurement of the mass difference between neutral charm-meson eigenstates. Allowing for
C
P
violation in mixing and in the interference between mixing and decay, the mass and decay-width differences are measured to be
x
C
P
=
[
3.97
±
0.46
(
stat
)
±
0.29
(
syst
)
]
Ă
1
0
â
3
and
y
C
P
=
[
4.59
±
1.20
(
stat
)
±
0.85
(
syst
)
]
Ă
1
0
â
3
, respectively. The
C
P
-violating parameters are measured as
Î
x
=
[
â
0.27
±
0.18
(
stat
)
±
0.01
(
syst
)
]
Ă
1
0
â
3
and
Î
y
=
[
0.20
±
0.36
(
stat
)
±
0.13
(
syst
)
]
Ă
1
0
â
3
. This is the first observation of a nonzero mass difference in the
D
0
meson system, with a significance exceeding seven standard deviations. The data are consistent with
C
P
symmetry and improve existing constraints on the associated parameters
Observation of excited Omega(0)(c) baryons in Omega(-)(b) -> Xi(+)(c) K-pi(-) decays
The first observation of the decay is
reported using collision data at centre-of-mass energies of 7, 8 and
13\, collected by the LHCb experiment, corresponding to an
integrated luminosity of 9\,. Four excited
baryons are observed in the mass projection of the decays with the significance of each exceeding five
standard deviations. They coincide with the states previously observed in
prompt \proton\proton and production. Relative production rates,
masses and natural widths of the states are measured, and a test of spin
hypotheses is performed. Moreover, the branching ratio of is measured relative to the decay mode and a precise measurement of the mass of
\mbox{} is obtained.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2021-012.html (LHCb
public pages
- âŠ