Study of the Physical Properties and Electrocaloric Effect in the BaTiO3 Nano- and Microceramics

The specific heat, thermal expansion, permittivity, and electrocaloric effect in bulk of BaTiO3 (BT) samples in the form of nano- (nBT-500 nm) and micro- (mBT-1200 nm) ceramics fabricated using spark plasma sintering and solid-state plasma techniques have been investigated. The size effect has been reflected, to a great extent, in the suppression of the specific heat and thermal expansion anomalies and in the changes in the temperatures and entropies of phase transitions and permittivity, and a decrease in the maximum intensive electrocaloric effect: ΔTmaxAD = 29 mK (E = 2.0 kV/cm) for nBT and ΔTmaxAD = 70 mK (E = 2.5 kV/cm) for mBT. The conductivity growth at temperatures above 360 K leads to the significant irreversible heating of the samples due to the Joule heat release in the applied electric field, which dominates over the electrocaloric effect

Dose-Dependent Effects of Nanoscale Forms of Humic Acids in a Hydroponic Culture of Triticum aestivum: Induction of Oxidative Stress and an Increase in the Number of Border Cells

В гидропонной культуре Triticum aestivum L. изучали биологическую активность гуминовых кислот в форме наночастиц размером 6,5 нм и 68 нм. Гуминовые наночастицы (мелкие и крупные) в изученных концентрациях не ингибировали рост корня и не вызывали деструктивных изменений корневого апекса 2-дневных проростков. На средах с гуминовыми наночастицами в корнях проростков наблюдалось дозозависимое увеличение содержания карбонилированных белков, малонового альдегида и пролина – маркеров индуцированного окислительного стресса. Для мелких наночастиц основным продуктом свободнорадикального окисления был малоновый диальдегид, для крупных – карбонилированные белки. Индуцированный гуминовыми наночастицами окислительный стресс сопровождался дозозависимым увеличением численности свободных пограничных клеток и размеров гелевого чехла в корневом апексе 2-дневных проростков. Для мелких наночастиц (6,5 нм) эти изменения были выражены в значительно большей степени, чем для крупных наночастиц (68 нм). Полученные результаты позволяют рассматривать гуминовые наночастицы в качестве адаптогенов: способствуя увеличению численности популяции пограничных клеток и системы гелевого чехла (как продукта экскреторной активности пограничных клеток), наночастицы увеличивают устойчивость корневого апекса к воздействию неблагоприятных биотических и абиотических факторовThe biological activity of humic acids in the form of nanoparticles with a size of 6.5 nm and 68 nm was studied in a hydroponic culture of Triticum aestivum L. Both smaller and larger humic nanoparticles at the studied concentrations neither inhibited root growth nor caused destructive changes in the root apexes of 2-day-old seedlings. A dose-dependent increase in the contents of markers of induced oxidative stress such as carbonylated proteins, malonaldehyde, and proline was observed in the roots of seedlings on media with humic nanoparticles. Malondialdehyde was the main product of free radical oxidation for smaller nanoparticles and carbonylated proteins – for larger ones. Oxidative stress induced by humic nanoparticles was accompanied by a dose-dependent increase in the number of free border cells and the size of the mucilaginous sheaths on the root apexes of 2-day-old seedlings. For smaller (6.5 nm) nanoparticles, these changes were much more pronounced than for larger (68 nm) nanoparticles. The results obtained allow us to consider humic nanoparticles as adaptogens: contributing to an increase in the population of border cells and the mucilaginous sheath system (as a product of the excretory activity of border cells), nanoparticles enhance the resistance of the root apex to the effects of unfavorable biotic and abiotic factor

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal

Measurement of tt̄ normalised multi-differential cross sections in pp collisions at √s = 13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

Normalised multi-differential cross sections for top quark pair (tt̄) production are measured in proton-proton collisions at a centre-of-mass energy of 13 TeV using events containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of 35.9fb⁻¹. The double-differential tt̄ cross section is measured as a function of the kinematic properties of the top quark and of the tt̄ system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the tt̄ system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength αS and the top quark pole mass (m_(pole_t) using several sets of parton distribution functions (PDFs). The measurement of m_(pole)_t exploits the sensitivity of the tt̄ invariant mass distribution to m_(pole)_t near the production threshold. Furthermore, a simultaneous fit of the PDFs, α_S, and m_(pole)_t is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of α_S and m_(pole)_t. The values α_S(m_Z) = 0.1135+0.0021−0.0017 and m_(pole)_t = 170.5±0.8GeV are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the tt̄ production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of m_(pole)_t of the order of +1 GeV, which can be regarded as additional theoretical uncertainty in the current m_(pole)_t extraction

Search for contact interactions and large extra dimensions in the dilepton mass spectra from proton-proton collisions at root s=13 TeV

A search for nonresonant excesses in the invariant mass spectra of electron and muon pairs is presented. The analysis is based on data from proton-proton collisions at a center-of-mass energy of 13 TeV recorded by the CMS experiment in 2016, corresponding to a total integrated luminosity of 36 fb(-1). No significant deviation from the standard model is observed. Limits are set at 95% confidence level on energy scales for two general classes of nonresonant models. For a class of fermion contact interaction models, lower limits ranging from 20 to 32 TeV are set on the characteristic compositeness scale . For the Arkani-Hamed, Dimopoulos, and Dvali model of large extra dimensions, the first results in the dilepton final state at 13 TeV are reported, and values of the ultraviolet cutoff parameter (T) below 6.9 TeV are excluded. A combination with recent CMS diphoton results improves this exclusion to (T) below 7.7 TeV, providing the most sensitive limits to date in nonhadronic final states.Peer reviewe

Search for vector-like quarks in events with two oppositely charged leptons and jets in proton-proton collisions at root s=13TeV

A search for the pair production of heavy vector-like partners T and B of the top and bottom quarks has been performed by the CMS experiment at the CERN LHC using proton-proton collisions at . The data sample was collected in 2016 and corresponds to an integrated luminosity of 35.9 production include those where one of the T quarks decays via TtZ and the other via TbW, tZ, or tH, where H is a Higgs boson. For the BB case, final states include those where one of the B quarks decays via BbZ and the other BtW, bZ, or bH. Events with two oppositely charged electrons or muons, consistent with coming from the decay of a Z boson, and jets are investigated. The number of observed events is consistent with standard model background estimations. Lower limits at 95% confidence level are placed on the masses of the T and B quarks for a range of branching fractions. Assuming 100% branching fractions for TtZ, and BbZ, T and B quark mass values below 1280 and 1130 respectively, are excluded.Peer reviewe

Constraints on anomalous HVV couplings from the production of Higgs bosons decaying to τ lepton pairs

A study is presented of anomalous HVV interactions of the Higgs boson, including its CP properties. The study uses Higgs boson candidates produced mainly in vector boson fusion and gluon fusion that subsequently decay to a pair of τ leptons. The data were recorded by the CMS experiment at the LHC in 2016 at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 35.9 fb$^{-1}$. A matrix element technique is employed for the analysis of anomalous interactions. The results are combined with those from the H → 4ℓ decay channel presented earlier, yielding the most stringent constraints on anomalous Higgs boson couplings to electroweak vector bosons expressed as effective cross section fractions and phases: the CP-violating parameter f$_{a3}$ cos(φ$_{a3}$)= (0.00 ± 0.27) × 10$^{-3}$ and the CP-conserving parameters f$_{a2}$ cos(φ$_{a2}$)= (0.08(+1.04/-0.21))× 10$^{-3}$, f$_{ Λ1}$ cos(φ$_{ Λ1}$) = (0.00(+0.53/-0.09) × 10$^{-3}$, and f (Zy/Λ1)cos(φ(Zy/ Λ1) = (0.0(+1.1/-1.3)) × 10$^{-3}$,. The current dataset does not allow for precise constraints on CP properties in the gluon fusion process. The results are consistent with standard model expectations

Search for supersymmetry in final states with photons and missing transverse momentum in proton-proton collisions at 13 TeV

Results are reported of a search for supersymmetry in final states with photons and missing transverse momentum in proton-proton collisions at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb(-1) collected at a center-of-mass energy of 13 TeV using the CMS detector. The results are interpreted in the context of models of gauge-mediated supersymmetry breaking. Production cross section limits are set on gluino and squark pair production in this framework. Gluino masses below 1.86 TeV and squark masses below 1.59 TeV are excluded at 95% confidence level.Peer reviewe