49 research outputs found
High-Utilisation Nanoplatinum Catalyst (Pt@cPIM) Obtained via Vacuum Carbonisation in a Molecularly Rigid Polymer of Intrinsic Microporosity
Polymers of intrinsic microporosity (PIM or here PIM-EA-TB) offer a highly rigid host environment into which hexachloroplatinate(IV) anions are readily adsorbed and vacuum carbonised (at 500 °C) to form active embedded platinum nanoparticles. This process is characterised by electron and optical microscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and electrochemical methods, which reveal that the PIM microporosity facilitates the assembly of nanoparticles of typically 1.0 to 2.5-nm diameter. It is demonstrated that the resulting carbonised âPt@cPIMâ from drop-cast films of ca. 550-nm average thickness, when prepared on tin-doped indium oxide (ITO), contain not only fully encapsulated but also fully active platinum nanoparticles in an electrically conducting hetero-carbon host. Alternatively, for thinner films (50â250 nm) prepared by spin coating, the particles become more exposed due to additional loss of the carbon host. In contrast to catalyst materials prepared by vacuum-thermolysed hexachloroplatinate(IV) precursor, the platinum nanoparticles within Pt@cPIM retain high surface area, electrochemical activity and high catalyst efficiency due to the molecular rigidity of the host. Data are presented for oxygen reduction, methanol oxidation and glucose oxidation, and in all cases, the high catalyst surface area is linked to excellent catalyst utilisation. Robust transparent platinum-coated electrodes are obtained with reactivity equivalent to bare platinum but with only 1 Όg Pt cmâ2 (i.e. ~100% active Pt nanoparticle surface is maintained in the carbonised microporous host). [Figure not available: see fulltext.
Enzyme classification with peptide programs: a comparative study
<p>Abstract</p> <p>Background</p> <p>Efficient and accurate prediction of protein function from sequence is one of the standing problems in Biology. The generalised use of sequence alignments for inferring function promotes the propagation of errors, and there are limits to its applicability. Several machine learning methods have been applied to predict protein function, but they lose much of the information encoded by protein sequences because they need to transform them to obtain data of fixed length.</p> <p>Results</p> <p>We have developed a machine learning methodology, called peptide programs (PPs), to deal directly with protein sequences and compared its performance with that of Support Vector Machines (SVMs) and BLAST in detailed enzyme classification tasks. Overall, the PPs and SVMs had a similar performance in terms of Matthews Correlation Coefficient, but the PPs had generally a higher precision. BLAST performed globally better than both methodologies, but the PPs had better results than BLAST and SVMs for the smaller datasets.</p> <p>Conclusion</p> <p>The higher precision of the PPs in comparison to the SVMs suggests that dealing with sequences is advantageous for detailed protein classification, as precision is essential to avoid annotation errors. The fact that the PPs performed better than BLAST for the smaller datasets demonstrates the potential of the methodology, but the drop in performance observed for the larger datasets indicates that further development is required.</p> <p>Possible strategies to address this issue include partitioning the datasets into smaller subsets and training individual PPs for each subset, or training several PPs for each dataset and combining them using a bagging strategy.</p
Observation of a resonant structure near the threshold in the decay
An amplitude analysis of the decay is carried out to
study for the first time its intermediate resonant contributions, using
proton-proton collision data collected with the LHCb detector at centre-of-mass
energies of 7, 8 and 13 TeV. A near-threshold peaking structure, referred to as
, is observed in the invariant-mass spectrum with
significance greater than 12 standard deviations. The mass, width and the
quantum numbers of the structure are measured to be MeV,
MeV and , respectively, where the first
uncertainties are statistical and the second systematic. The properties of the
new structure are consistent with recent theoretical predictions for a state
composed of quarks. Evidence for an additional structure is
found around 4140 MeV in the invariant mass, which might be
caused either by a new resonance with the assignment or by a coupled-channel effect.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-018.html (LHCb
public pages
A new class of glycomimetic drugs to prevent free fatty acid-induced endothelial dysfunction
Background: Carbohydrates play a major role in cell signaling in many biological processes. We have developed a set of glycomimetic drugs that mimic the structure of carbohydrates and represent a novel source of therapeutics for endothelial dysfunction, a key initiating factor in cardiovascular complications. Purpose: Our objective was to determine the protective effects of small molecule glycomimetics against free fatty acidÂinduced endothelial dysfunction, focusing on nitric oxide (NO) and oxidative stress pathways. Methods: Four glycomimetics were synthesized by the stepwise transformation of 2,5Âdihydroxybenzoic acid to a range of 2,5Âsubstituted benzoic acid derivatives, incorporating the key sulfate groups to mimic the interactions of heparan sulfate. Endothelial function was assessed using acetylcholineÂinduced, endotheliumdependent relaxation in mouse thoracic aortic rings using wire myography. Human umbilical vein endothelial cell (HUVEC) behavior was evaluated in the presence or absence of the free fatty acid, palmitate, with or without glycomimetics (1”M). DAFÂ2 and H2DCFÂDA assays were used to determine nitric oxide (NO) and reactive oxygen species (ROS) production, respectively. Lipid peroxidation colorimetric and antioxidant enzyme activity assays were also carried out. RTÂPCR and western blotting were utilized to measure Akt, eNOS, NrfÂ2, NQOÂ1 and HOÂ1 expression. Results: Ex vivo endotheliumÂdependent relaxation was significantly improved by the glycomimetics under palmitateÂinduced oxidative stress. In vitro studies showed that the glycomimetics protected HUVECs against the palmitateÂinduced oxidative stress and enhanced NO production. We demonstrate that the protective effects of preÂincubation with glycomimetics occurred via upregulation of Akt/eNOS signaling, activation of the Nrf2/ARE pathway, and suppression of ROSÂinduced lipid peroxidation. Conclusion: We have developed a novel set of small molecule glycomimetics that protect against free fatty acidinduced endothelial dysfunction and thus, represent a new category of therapeutic drugs to target endothelial damage, the first line of defense against cardiovascular disease
Search for rare decays of D0 mesons into two muons
A search for the very rare
D
0
â
Ό
+
Ό
â
decay is performed using data collected by the LHCb experiment in proton-proton collisions at
â
s
=
7
, 8, and 13 TeV, corresponding to an integrated luminosity of
9
â
â
fb
â
1
. The search is optimized for
D
0
mesons from
D
*
+
â
D
0
Ï
+
decays but is also sensitive to
D
0
mesons from other sources. No evidence for an excess of events over the expected background is observed. An upper limit on the branching fraction of this decay is set at
B
(
D
0
â
Ό
+
Ό
â
)
<
3.1
Ă
10
â
9
at a 90% C.L. This represents the worldâs most stringent limit, constraining models of physics beyond the standard model
Direct CP violation in charmless three-body decays of B± mesons
Measurements of
C
P
asymmetries in charmless three-body decays of
B
±
mesons are reported using proton-proton collision data collected by the LHCb detector, corresponding to an integrated luminosity of
5.9
â
â
fb
â
1
. The previously observed
C
P
asymmetry in
B
±
â
Ï
±
K
+
K
â
decays is confirmed, and
C
P
asymmetries are observed with a significance of more than five standard deviations in the
B
±
â
Ï
±
Ï
+
Ï
â
and
B
±
â
K
±
K
+
K
â
decays, while the
C
P
asymmetry of
B
±
â
K
±
Ï
+
Ï
â
decays is confirmed to be compatible with zero. The distributions of these asymmetries are also studied as a function of the three-body phase space and suggest contributions from rescattering and resonance interference processes. An indication of the presence of the decays
B
±
â
Ï
±
Ï
c
0
(
1
P
)
in both
B
±
â
Ï
±
Ï
+
Ï
â
and
B
±
â
Ï
±
K
+
K
â
decays is observed, as is
C
P
violation involving these amplitudes
Measurement of antiproton production from antihyperon decays in p He collisions at âsNN = 110 GeV
The interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between primary cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5TeV incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and 110GeV. The dominant antihyperon contribution, namely ÎÂŻâpÂŻÏ+ decays from promptly produced ÎÂŻ particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models
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Searches for rare B-s(0) and B-0 decays into four muons
Searches for rare and decays into four muons are performed
using proton-proton collision data recorded by the LHCb experiment,
corresponding to an integrated luminosity of 9 . Direct decays
and decays via light scalar and resonances are considered. No evidence
for the six decays searched for is found and upper limits at the 95% confidence
level on their branching fractions ranging between and
are set
First measurement of the ZâÎŒ+ÎŒâ angular coefficients in the forward region of pp collisions at âs = 13 TeV
The first study of the angular distribution of
Ό
+
Ό
â
pairs produced in the forward rapidity region via the Drell-Yan reaction
p
p
â
Îł
â
/
Z
+
X
â
â
+
â
â
+
X
is presented, using data collected with the LHCb detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of
5.1
â
â
fb
â
1
. The coefficients of the five leading terms in the angular distribution are determined as a function of the dimuon transverse momentum and rapidity. The results are compared to various theoretical predictions of the
Z
-boson production mechanism and can also be used to probe transverse-momentum-dependent parton distributions within the proton