We present the new parton distribution functions (PDFs) from the CTEQ-TEA collaboration, obtained using a wide variety of high-precision Large Hadron Collider (LHC) data, in addition to the combined ...HERA I + II deep-inelastic scattering dataset, along with the datasets present in the CT14 global QCD analysis. New LHC measurements in single-inclusive jet production with the full rapidity coverage, as well as production of Drell-Yan pairs, top-quark pairs, and high-pT Z bosons, are included to achieve the greatest sensitivity to the PDFs. The parton distributions are determined at next-to-leading order and next-to-next-to-leading order, with each of these PDFs accompanied by error sets determined using the Hessian method. Fast PDF survey techniques, based on the Hessian representation and the Lagrange multiplier method, are used to quantify the preference of each data set to quantities such as αs(mZ), and the gluon and strange quark distributions. We designate the main resulting PDF set as CT18. The ATLAS 7 TeV precision W / Z data are not included in CT18, due to their tension with other datasets in the global fit. Alternate PDF sets are generated including the ATLAS precision 7 TeV W / Z data (CT18A), a new scale choice for low- x DIS data (CT18X), or all of the above with a slightly higher choice for the charm mass (CT18Z). Theoretical calculations of standard candle cross sections at the LHC (such as the g g fusion Higgs boson cross section) are presented.
Posttranslational modification of a protein, either alone or in combination with other modifications, can control properties of that protein, such as enzymatic activity, localization, stability, or ...interactions with other molecules.
-ε-Lysine acetylation is one such modification that has gained attention in recent years, with a prevalence and significance that rival those of phosphorylation. This review will discuss the current state of the field in bacteria and some of the work in archaea, focusing on both mechanisms of
-ε-lysine acetylation and methods to identify, quantify, and characterize specific acetyllysines. Bacterial
-ε-lysine acetylation depends on both enzymatic and nonenzymatic mechanisms of acetylation, and recent work has shed light into the regulation of both mechanisms. Technological advances in mass spectrometry have allowed researchers to gain insight with greater biological context by both (i) analyzing samples either with stable isotope labeling workflows or using label-free protocols and (ii) determining the true extent of acetylation on a protein population through stoichiometry measurements. Identification of acetylated lysines through these methods has led to studies that probe the biological significance of acetylation. General and diverse approaches used to determine the effect of acetylation on a specific lysine will be covered.
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Schematic procedure for the preparation of GN/MIPs/GCE and our concept for selective electrochemical detection of IDP.
•Uniform MIP monolayers were loaded on inert graphene surface ...using a novel strategy.•Interesting factors were discussed to efficiently control the synthesis process.•The procedures were greatly simplified to cut down the cost and improve the stability.•Adsorption isotherm and kinetics study were carried out to explain the mechanism.•The proposed sensor was successfully applied in real rice samples.
A novel and simple imprinting route based on graphene (GN) was proposed to fabricate an electrochemical sensor for sensitive and selective determination of imidacloprid (IDP) residue. In this route, p-vinylbenzoic acid (VBA) was utilized as functional monomer to immobilize onto GN in N,N-dimethylformamide (DMF) solvent via π-π interaction, directing the polymerization of uniform molecularly imprinted polymers (MIP) layers on the surface of GN sheets. Besides, quantitative control of the synthesis of MIP/GN and the preparation of MIP/GN modified glassy carbon electrode (GCE) were carried out, which were rarely found in other papers. Thus, the proposed sensor possesses highly improved stability and specific recognition ability. The adsorption isotherm study indicated that the MIP layer on GN surface is monolayer and the structure is homogeneous. The peak current of IDP on MIP/GN modified GCE is linear with IDP concentration in the range of 0.5–15μM with a detection limit of 0.10μM. In addition, the novel method was further applied to detect IDP in brown rice samples with satisfactory results.
Abstract The Parkes 20 cm multibeam pulsar surveys have discovered nearly half of the known pulsars and revealed many distant pulsars with high dispersion measures. Using a sample of 1301 pulsars ...from these surveys, we have explored the spatial distribution and birth rate of normal pulsars. The pulsar distances used to calculate the pulsar surface density are estimated from the YMW16 electron-density model. When estimating the impact of the Galactic background radiation on our survey, we projected pulsars in the galaxy onto the Galactic plane, assuming that the flux density distribution of pulsars is uniform in all directions, and utilized the most up-to-date background temperature map. We also used an up-to-date version of the ATNF Pulsar Catalogue to model the distribution of pulsar flux densities at 1400 MHz. We derive an improved radial distribution for the pulsar surface density projected onto the Galactic plane, which has a maximum value at ∼4 kpc from the Galactic center. We also derive the local surface density and birth rate of pulsars, obtaining 47 ± 5 kpc −2 and ∼4.7 ± 0.5 kpc −2 Myr −1 , respectively. For the total number of potentially detectable pulsars in the galaxy, we obtain (1.1 ± 0.2) × 10 4 and (1.1 ± 0.2)×10 5 before and after applying the Tauris & Manchester beaming correction model. The radial distribution function is used to estimate the proportion of pulsars in each spiral arm and the Galactic center.
The photon content of the neutron Xie, Keping; Zhou, Bei; Hobbs, T. J.
The journal of high energy physics,
04/2024, Letnik:
2024, Številka:
4
Journal Article
Recenzirano
Odprti dostop
A
bstract
In this work, we complete our CT18qed study with the neutron’s photon parton distribution function (PDF), which is essential for the nucleus scattering phenomenology. Two methods, CT18lux ...and CT18qed, based on the LUXqed formalism and the DGLAP evolution, respectively, to determine the neutron’s photon PDF have been presented. Various low-
Q
2
non-perturbative variations have been carefully examined, which are treated as additional uncertainties on top of those induced by quark and gluon PDFs. The impacts of the momentum sum rule as well as isospin symmetry violation have been explored and turned out to be negligible. A detailed comparison with other neutron’s photon PDF sets has been performed, which shows a great improvement in the precision and a reasonable uncertainty estimation. Finally, two phenomenological implications are demonstrated with photon-initiated processes: neutrino-nucleus
W
-boson production, which is important for the near-future TeV–PeV neutrino observations, and the axion-like particle production at a high-energy muon beam-dump experiment.
Abstract
We report the observations of periodic nulling in PSR B2111+46 at 1250 MHz with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The nulling fractions (NF) as well as ...nulling period of this pulsar were calculated. The NF and nulling period are 17% ± 1% and 62.49 ± 0.99
P
1
, respectively, and the periodic nulling shows variations in periodicity with time. The durations of each consecutive burst and nulling were investigated, which show that the power-law distribution and the indices are −1.11 ± 0.04 and −2.08 ± 0.23. In the observed frequency band, the width of the profile is narrowed with the increase in frequency, and the degree of polarization has no obvious trend with the increase in frequency. We discovered a weak emission component in front of the leading component of this triple-type profile pulsar that was not observed in other bands and by other telescopes. With the fitting of rotation vector model, we obtained that the angles of the magnetic inclination
α
and the line of sight
ζ
are ∼13.°0 and ∼11.°6, respectively. The high-sensitivity observation of FAST improves our understanding of the emission of this pulsar.
To assess the current status of climate models in simulating clouds, basic cloud climatologies from ten atmospheric general circulation models are compared with satellite measurements from the ...International Satellite Cloud Climatology Project (ISCCP) and the Clouds and Earth's Radiant Energy System (CERES) program. An ISCCP simulator is employed in all models to facilitate the comparison. Models simulated a four‐fold difference in high‐top clouds. There are also, however, large uncertainties in satellite high thin clouds to effectively constrain the models. The majority of models only simulated 30–40% of middle‐top clouds in the ISCCP and CERES data sets. Half of the models underestimated low clouds, while none overestimated them at a statistically significant level. When stratified in the optical thickness ranges, the majority of the models simulated optically thick clouds more than twice the satellite observations. Most models, however, underestimated optically intermediate and thin clouds. Compensations of these clouds biases are used to explain the simulated longwave and shortwave cloud radiative forcing at the top of the atmosphere. Seasonal sensitivities of clouds are also analyzed to compare with observations. Models are shown to simulate seasonal variations better for high clouds than for low clouds. Latitudinal distribution of the seasonal variations correlate with satellite measurements at >0.9, 0.6–0.9, and −0.2–0.7 levels for high, middle, and low clouds, respectively. The seasonal sensitivities of cloud types are found to strongly depend on the basic cloud climatology in the models. Models that systematically underestimate middle clouds also underestimate seasonal variations, while those that overestimate optically thick clouds also overestimate their seasonal sensitivities. Possible causes of the systematic cloud biases in the models are discussed.
Infectious diseases are intimately associated with the dynamics of biodiversity. However, the role that infectious disease plays within ecological communities is complex. The complex effects of ...infectious disease at the scale of communities and ecosystems are driven by the interaction between host and pathogen. Whether or not a given host–pathogen interaction results in progression from infection to disease is largely dependent on the physiological characteristics of the host within the context of the external environment. Here, we highlight the importance of understanding the outcome of infection and disease in the context of host ecophysiology using amphibians as a model system. Amphibians are ideal for such a discussion because many of their populations are experiencing declines and extinctions, with disease as an important factor implicated in many declines and extinctions. Exposure to pathogens and the host's responses to infection can be influenced by many factors related to physiology such as host life history, immunology, endocrinology, resource acquisition, behaviour and changing climates. In our review, we discuss the relationship between disease and biodiversity. We highlight the dynamics of three amphibian host–pathogen systems that induce different effects on hosts and life stages and illustrate the complexity of amphibian–host–parasite systems. We then review links between environmental stress, endocrine–immune interactions, disease and climate change.
Four dimensional scanning transmission electron microscopy (4D STEM) records the scattering of electrons in a material in great detail. The benefits offered by 4D STEM are substantial, with the ...wealth of data it provides facilitating for instance high precision, high electron dose efficiency phase imaging via centre of mass or ptychography based analysis. However the requirement for a 2D image of the scattering to be recorded at each probe position has long placed a severe bottleneck on the speed at which 4D STEM can be performed. Recent advances in camera technology have greatly reduced this bottleneck, with the detection efficiency of direct electron detectors being especially well suited to the technique. However even the fastest frame driven pixelated detectors still significantly limit the scan speed which can be used in 4D STEM, making the resulting data susceptible to drift and hampering its use for low dose beam sensitive applications. Here we report the development of the use of an event driven Timepix3 direct electron camera that allows us to overcome this bottleneck and achieve 4D STEM dwell times down to 100 ns; orders of magnitude faster than what has been possible with frame based readout. We characterize the detector for different acceleration voltages and show that the method is especially well suited for low dose imaging and promises rich datasets without compromising dwell time when compared to conventional STEM imaging.
•Event driven Timepix3 based camera demonstrated for use in 4D STEM.•The event driven architecture accelerates 4D STEM dwell times down to 100 ns.•Bottleneck 4D STEM acquisition speed shifted from camera to scan coils.•Focused probe 4D STEM benefits from both increased precision and ease for low doses.
Records of the Ediacaran carbon cycle (635–541 million years ago) include the Shuram excursion (SE), the largest negative carbonate carbon isotope excursion in Earth history (down to −12‰). The ...nature of this excursion remains enigmatic given the difficulties of interpreting a perceived extreme global decrease in the δ13C of seawater dissolved inorganic carbon. Here, we present carbonate and organic carbon isotope (δ13Ccarb and δ13Corg) records from the Ediacaran Doushantuo Formation along a proximal‐to‐distal transect across the Yangtze Platform of South China as a test of the spatial variation of the SE. Contrary to expectations, our results show that the magnitude and morphology of this excursion and its relationship with coexisting δ13Corg are highly heterogeneous across the platform. Integrated geochemical, mineralogical, petrographic, and stratigraphic evidence indicates that the SE is a primary marine signature. Data compilations demonstrate that the SE was also accompanied globally by parallel negative shifts of δ34S of carbonate‐associated sulfate (CAS) and increased 87Sr/86Sr ratio and coastal CAS concentration, suggesting elevated continental weathering and coastal marine sulfate concentration during the SE. In light of these observations, we propose a heterogeneous oxidation model to explain the high spatial heterogeneity of the SE and coexisting δ13Corg records of the Doushantuo, with likely relevance to the SE in other regions. In this model, we infer continued marine redox stratification through the SE but with increased availability of oxidants (e.g., O2 and sulfate) limited to marginal near‐surface marine environments. Oxidation of limited spatiotemporal extent provides a mechanism to drive heterogeneous oxidation of subsurface reduced carbon mostly in shelf areas. Regardless of the mechanism driving the SE, future models must consider the evidence for spatial heterogeneity in δ13C presented in this study.
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