821 research outputs found
Sensitivity to triple Higgs couplings via di-Higgs production in the 2HDM at the (HL-)LHC
An important task of the LHC is the investigation of the Higgs-boson sector. Of particular interest is the reconstruction of the Higgs potential, i.e. the measurement of the Higgs self-couplings. Based on previous analyses, within the 2HDMs type~I and~II, we analyze several two-dimensional benchmark planes that are over large parts in agreement with all theoretical and experimental constraints. For these planes we evaluate di-Higgs production cross sections at the (HL-)LHC with a center-of-mass energy of 13 TeV at NLO in the heavy top-quark limit with the code HPAIR. We investige in particular the process , with h being the Higgs boson discovered at the LHC with a mass of about 125 GeV. The top box diagram of the loop-mediated gluon fusion process into Higgs pairs interferes with the s-channel exchange of the two CP-even 2HDM Higgs bosons h and H involving the trilinear couplings λ and λ, respectively. Depending on the size of the involved top-Yukawa and triple Higgs couplings as well as on the mass of H, the contribution of the s-channel H~diagram can be dominating or be highly suppressed. We find regions of the allowed parameter space in which the di-Higgs production cross section can differ by many standard deviations from its SM prediction, indicating possible access to deviations in λ from the SM value λ and/or contributions involving λ. The sensitivity to λ is further analyzed employing the mhh distributions. We demonstrate how a possible measurement of λ depends on the various experimenal uncertainties. Depending on the underlying parameter space, the HL-LHC may have the option not only to detect beyond-the-Standard-Model triple Higgs couplings, but also to provide a first rough measurement of their sizes
Sensitivity to triple Higgs couplings via di-Higgs production in the 2HDM at the (HL-)LHC
An important task of the LHC is the investigation of the Higgs-boson sector. Of particular interest is the reconstruction of the Higgs potential, i.e. the measurement of the Higgs self-couplings. Based on previous analyses, within the 2-Higgs-Doublet Model (2HDM) type I, we analyze several two-dimensional benchmark planes that are over large parts in agreement with all theoretical and experimental constraints. For these planes we evaluate di-Higgs production cross sections at the (HL-)LHC with a center-of-mass energy of 14 TeV at next-to-leading order in the heavy top-quark limit with the code HPAIR. We investigate in particular the process , with h being the Higgs boson discovered at the LHC with a mass of about 125 GeV. The top box diagram of the loop-mediated gluon fusion process into Higgs pairs interferes with the s-channel exchange of the two -even 2HDM Higgs bosons h and H . The latter two involve the triple Higgs couplings (THCs) λ and λ , respectively, possibly making them accessible at the HL-LHC. Depending on the size of the involved top-Yukawa and THCs as well as on the mass of H , the contribution of the s-channel H diagram can be dominating or be highly suppressed. We find regions of the allowed parameter space in which the di-Higgs production cross section can differ by many standard deviations from its SM prediction, indicating possible access to deviations in λ from the SM value λ and/or contributions involving λ. The sensitivity to the beyond-the-SM (BSM) THC λ is further analyzed employing the distributions. We demonstrate how a possible measurement of λ depends on the various experimental uncertainties. Depending on the underlying parameter space, the HL-LHC may have the option not only to detect BSM THCs, but also to provide a first rough measurement of their sizes
Strain- and Adsorption-Dependent Electronic States and Transport or Localization in Graphene
The chapter generalizes results on influence of uniaxial strain and
adsorption on the electron states and charge transport or localization in
graphene with different configurations of imperfections (point defects):
resonant (neutral) adsorbed atoms either oxygen- or hydrogen-containing
molecules or functional groups, vacancies or substitutional atoms, charged
impurity atoms or molecules, and distortions. To observe electronic properties
of graphene-admolecules system, we applied electron paramagnetic resonance
technique in a broad temperature range for graphene oxides as a good basis for
understanding the electrotransport properties of other active carbons. Applied
technique allowed observation of possible metal-insulator transition and
sorption pumping effect as well as discussion of results in relation to the
granular metal model. The electronic and transport properties are calculated
within the framework of the tight-binding model along with the Kubo-Greenwood
quantum-mechanical formalism. Depending on electron density and type of the
sites, the conductivity for correlated and ordered adsorbates is found to be
enhanced in dozens of times as compared to the cases of their random
distribution. In case of the uniaxially strained graphene, the presence of
point defects counteracts against or contributes to the band-gap opening
according to their configurations. The band-gap behaviour is found to be
nonmonotonic with strain in case of a simultaneous action of defect ordering
and zigzag deformation. The amount of localized charge carriers (spins) is
found to be correlated with the content of adsorbed centres responsible for the
formation of potential barriers and, in turn, for the localization effects.
Physical and chemical states of graphene edges, especially at a uniaxial strain
along one of them, play a crucial role in electrical transport phenomena in
graphene-based materials.Comment: 16 pages, 10 figure
Oxidation resistance Cr-Al steels and calculation of parametric diagrams
У роботі розглянуті питання окалиностійкості сталей із різним вмістом хрому та алюмінію за високих температур. Розроблено методику визначення оптимального хімічного складу жаростійких хромоалюмінієвих сталей залежно від температурних умов і тривалості експлуатації литих деталей. Побудовані параметричні діаграми для визначення окалиностійкості і терміну експлуатації виробів із хромоалюмінієвих сталей. Розроблені моделі дозволяють прогнозувати окалиностійкість сталей із різними концентраціями хрому та алюмінію.In work there are the considered questions of oxidation resistance steels at different temperatures with a different maintenance of chrome and aluminums. Conformity to the law of oxidization of heat-resistant is explored steels in different gases environment. It is set that the heated air is more aggressive environment with the additive 45% of aquatic steam. The increase maintenance of chrome from 18 to 30% results in diminishment of losses of mass from 15 to 5 мг/см². Addition of aluminums to chromic steels also brings to the increase of oxidation resistance studied over steels. Thus, maybe, that became containing of more than a 25% chrome with the addition 2…3% of aluminums has perspective development. For the decline of Saving energy costs and time as mathematical treatment construction of the developed models diagrams was used. The developed method allows to determine different optimum chemical compositions of heat-resistant Cr-Al steels depending on temperature terms and duration of exploitation of the poured details. The developed models allow to determine oxidation resistance and terms of exploitation of Cr-Al steels. The developed models allow with high authenticity to forecast oxidation resistance steels with different concentrations of chrome and aluminums.В работе рассмотренные вопросы окалиностойкости сталей при различных температурах с разным содержанием хрома и алюминия. Разработанно методику определения оптимального химического состава жаростойких хромоалюминиевых сталей в зависимости от температурных условий и длительности эксплуатации литых деталей. Построенно параметрические диаграммы для определения окалиностойкости и сроков эксплуатации хромоалюминиевых сталей. Разработанные модели позволяют прогнозировать окалиностойкисть сталей с различными концентрациями хрома и алюминия
Assessment of soil erosion rate trends in two agricultural regions of European Russia for the last 60 years
© 2018, Springer-Verlag GmbH Germany, part of Springer Nature. Purpose: Forest–steppe and the southern forest ecotones of European Russia (ER) are the most productive agricultural areas in Russia. Both climate and land use changes have occurred within the ER during last 30 years. These changes can lead to changes in the timing, magnitude, and spatial distribution of soil erosion rates on cultivated lands. The objective of this research was to assess the trends in soil erosion rates since the 1960s for two agricultural regions of ER. Materials and methods: Rates of soil erosion were estimated for two time windows (1963–1986 and 1986–2015) within the two agricultural regions. Both regions are characterized by a high proportion of cropland (> 60%), and within each region, one river basin and one 1st–3rd-order agricultural catchment were selected for a detailed assessment of soil erosion rates. Erosion models and visual interpretation of satellite images were used for the evaluation of the erosion rates for the river basins. Sediment budget assessments, 137Cs dating, geomorphologic mapping, and erosion models were used for the evaluation of the sediment redistribution for the two time windows in agricultural catchments. Results and discussion: At the river basin scale, the mean annual erosion rate did not change in the western part of forest–steppe ecotone; however, there was a weak negative trend in the mean annual erosion rate for the eastern part of the southern forest ecotone. A large negative trend in the erosion rate was found for both small agricultural catchments. In all cases, the reduction in the erosion rates was mainly associated with a decrease of surface runoff during snowmelt, as a result of an increase in both the air and soil temperatures during winter season. The soil loss reduction during snowmelt was counteracted by an equal increase in rainfall erosion due to increase of rainfall intensity in western part of forest–steppe ecotone. Conclusions: Reduction of surface runoff during spring snowmelt was the main reason the erosion rates declined on cultivated lands within the forest–steppe and southern forest ecotones of ER. Evaluation of ephemeral gully erosion rate was not incorporated into State Hydrological Institute erosion model used for the evaluation of the soil losses during snowmelt. This has led to an underestimation of the total soil losses for the 1963–1986 time window for all study sites
57Co Production using RbCl/RbCl/58Ni Target Stacks at the Los Alamos Isotope Production Facility: LA-UR-14-22122
Introduction
The Los Alamos Isotope Production Program commonly irradiates target stacks consisting of high, medium and low-energy targets in the
“A-”, “B-”, and “C-slots”, respectively, with a 100MeV proton beam. The Program has recently considered the production of 57Co (t1/2 = 271.74 d, 100% EC) from 58Ni using the low-energy posi-tion of the Isotope Production Facility, down-stream of two RbCl salt targets. Initial MCNPX/ CINDER’90 studies predicted 57Co radioisotopic purities >90% depending on time allotted for decay. But these studies do not account for broadening of the proton beam’s energy distribution caused by density changes in molten, potentially boiling RbCl targets upstream of the 58Ni (see e.g., [1]). During a typical production with 230 µA average proton intensity, the RbCl targets’ temperature is expected to produce beam energy changes of several MeV and commensurate effects on the yield and purity of any radioisotope irradiated in the low-energy posi-tion of the target stack. An experiment was designed to investigate both the potential for 57Co’s large-scale production and the 2-dimensional proton beam energy distribution.
Material and Methods
Two aluminum targets holders were fabricated to each contain 31 58Ni discs (99.48%, Isoflex, CA), 4.76 mm (Φ) x 0.127 mm (thickness). Each foil was indexed with a unique cut pattern by EDM with a 0.254 mm brass wire to allow their position in the target to be tracked through hot cell disassembly and assay (see FIG. 1). Brass residue from EDM was removed with HNO3/HCl solution. The holders’ front windows were 2.87 and 1.37 mm thick, corresponding to predicted average incident energies of 17.9 and 24.8 MeV on the Ni [2].
Each target was irradiated with protons for 1 h with an average beam current of 218 ± 3 µA to ensure an upstream RbCl target temperature and density that would mimic routine production. Following irradiation, targets were disassembled and each disc was assayed by HPGe γ-spectroscopy. Residuals 56Co (t1/2 = 77.2 d, 100% EC) and 57Co have inversely varying measured nuclear formation cross sections between approximately 15 and 40 MeV.
Results and Conclusion
Distributions of 56,57,58,60Co were tracked as described in both irradiated targets.
The distribution of activities matched expectations, with radioisotopes produced by proton interactions with the 58Ni target (56Co and 57Co) concentrated in the area struck by IPF’s rastered, annulus-shaped proton beam, and the distribution of radioisotopes produced by neutron-induced reactions (58Co and 60Co) relatively uniform across all irradiated foils. The potential range of such temperature variations predicted by thermal modeling (approx. ± 200 °C) corre-sponds to a density variation of nearly 0.2 g.cm−3, and a change in the average energy of protons incident on the low-energy “C-slot” of approximately 5 MeV, well-matched to the indi-rectly measured energy variation plotted in FIG. 3. No energy distribution in the plane per-pendicular to the beam axis has previously been assumed in the design of IPF targets.
The effective incident energy measured by yields of 57Co and 56Co is, however, almost 5 MeV higher than those predicted using Anderson and Ziegler’s well-known formalism [2]. This discrepancy is supported by previous reports [3] and likely exacerbated compared to these reports by the large magnitude of energy degradation (from 100 MeV down to 30 MeV) in the IPF target stack. For more detailed discussion, refer to Marus et al.’s abstract, also reported at this meeting. While the experiments reported do confirm the potential for many Ci-scale yields of 57Co from months-long irradiations at the IPF, the level radioisotopic impurities 56Co and 58Co are concerning. Commercial radioisotope producers using U-150 (23 MeV) and RIC-14 (14 MeV) cyclotrons in Obninsk, Russia specify 56/58Co activities at levels <0.2% of available 57C
Radiolabeling of a polypeptide polymer for intratumoral delivery of alpha-particle emitter, 225Ac, and beta-particle emitter, 177Lu
INTRODUCTION\nMETHODS\nRESULTS\nCONCLUSION\nRadiotherapy of cancer requires both alpha- and beta-particle emitting radionuclides, as these radionuclide types are efficient at destroying different types of tumors. Both classes of radionuclides require a vehicle, such as an antibody or a polymer, to be delivered and retained within the tumor. Polyglutamic acid (pGlu) is a polymer that has proven itself effective as a basis of drug-polymer conjugates in the clinic, while its derivatives have been used for pretargeted tumor imaging in a research setup. trans-Cyclooctene (TCO) modified pGlu is suitable for pretargeted imaging or therapy, as well as for intratumoral radionuclide therapy. In all cases, it becomes indirectly radiolabeled via the bioorthogonal click reaction with the tetrazine (Tz) molecule carrying the radionuclide. In this study, we report the radiolabeling of TCO-modified pGlu with either lutetium-177 (177Lu), a beta-particle emitter, or actinium-225 (225Ac), an alpha-particle emitter, using the click reaction between TCO and Tz.\nA panel of Tz derivatives containing a metal ion binding chelator (DOTA or macropa) connected to the Tz moiety directly or through a polyethylene glycol (PEG) linker was synthesized and tested for their ability to chelate 177Lu and 225Ac, and click to pGlu-TCO. Radiolabeled 177Lu-pGlu and 225Ac-pGlu were isolated by size exclusion chromatography. The retention of 177Lu or 225Ac by the obtained conjugates was investigated in vitro in human serum.\nAll DOTA-modified Tzs efficiently chelated 177Lu resulting in average radiochemical conversions (RCC) of >75%. Isolated radiochemical yields (RCY) for 177Lu-pGlu prepared from 177Lu-Tzs ranged from 31% to 55%. TLC analyses detected 177Lu for all 177Lu-pGlu preparations over six days in human serum. For 225Ac chelation, optimized RCCs ranged from 61 ± 34% to quantitative for DOTA-Tzs and were quantitative for the macropa-modified Tz (>98%). Isolated radiochemical yields (RCY) for 225Ac-pGlu prepared from 225Ac-Tzs ranged from 28% to 51%. For 3 out of 5 225Ac-pGlu conjugates prepared from DOTA-Tzs, the amount of unchelated 225Ac stayed below 10% over six days in human serum, while 225Ac-pGlu prepared from macropa-Tz showed a steady release of up to 37% 225Ac.\nWe labeled TCO-modified pGlu polymers with alpha- and beta-emitting radionuclides in acceptable RCYs. All 177Lu-pGlu preparations and some 225Ac-pGlu preparations showed excellent stability in human plasma. Our work shows the potential of pGlu as a vehicle for alpha- and beta-radiotherapy of tumors and demonstrated the usefulness of Tz ligation for indirect radiolabeling.Drug Delivery Technolog
Charged-Particle Multiplicity in Proton-Proton Collisions
This article summarizes and critically reviews measurements of
charged-particle multiplicity distributions and pseudorapidity densities in
p+p(pbar) collisions between sqrt(s) = 23.6 GeV and sqrt(s) = 1.8 TeV. Related
theoretical concepts are briefly introduced. Moments of multiplicity
distributions are presented as a function of sqrt(s). Feynman scaling, KNO
scaling, as well as the description of multiplicity distributions with a single
negative binomial distribution and with combinations of two or more negative
binomial distributions are discussed. Moreover, similarities between the energy
dependence of charged-particle multiplicities in p+p(pbar) and e+e- collisions
are studied. Finally, various predictions for pseudorapidity densities, average
multiplicities in full phase space, and multiplicity distributions of charged
particles in p+p(pbar) collisions at the LHC energies of sqrt(s) = 7 TeV, 10
TeV, and 14 TeV are summarized and compared.Comment: Invited review for Journal of Physics G -- version 2: version after
referee's comment
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