Prompt neutrinos and intrinsic charm at SHiP

We present a new evaluation of the far-forward neutrino plus antineutrino flux and number of events from charm hadron decays in a 400 GeV proton beam dump experiment like the Search for Hidden Particles (SHiP). Using next-to-leading order perturbative QCD and a model for intrinsic charm, we include intrinsic transverse momentum effects and other kinematic angular corrections. We compare this flux to a far-forward flux evaluated with next-to-leading order perturbative QCD, without intrinsic transverse momentum, that used the angular distribution of charm quarks rather than the neutrinos from their decays. The tau neutrino plus antineutrino number of events in the perturbative QCD evaluation is reduced by a factor of about three when intrinsic transverse momentum and the full decay kinematics are included. We show that intrinsic charm contributions can significantly enhance the number of events from neutrinos from charm hadron decays. Measurements of the number of events from tau neutrino plus antineutrino interactions and of the muon charge asymmetry as a function of energy can be used to constrain intrinsic charm models.Comment: 39 pages, 18 figures; v2 with revisions of text for clarity, version to be published in JHE

Forward production of prompt neutrinos from charm in the atmosphere and at high energy colliders

The high-energy atmospheric neutrino flux is dominated by neutrinos from the decays of charmed hadrons produced in the forward direction by cosmic ray interactions with air nuclei. We evaluate the charm contributions to the prompt atmospheric neutrino flux as a function of the center-of-mass energy $\sqrt{s}$ of the hadronic collision and of the center-of-mass rapidity $y$ of the produced charm hadron. Uncertainties associated with parton distribution functions are also evaluated as a function of $y$. We find that the $y$ coverage of LHCb for forward heavy-flavour production, complemented by the angular coverage of present and future forward neutrino experiments at the LHC, bracket the most interesting $y$ regions for the prompt atmospheric neutrino flux. At $\sqrt{s}=14$ TeV foreseen for the HL-LHC phase, nucleon collisions in air contribute to the prompt neutrino flux prominently below $E_\nu\sim 10^7$~GeV. Measurements of forward charm and/or forward neutrinos produced in hadron collisions up to $\sqrt{s}=100$ TeV, which might become possible at the FCC, are relevant for the prompt atmospheric neutrino flux up to $E_\nu=10^8$ GeV and beyond.Comment: 29 pages, 11 figure

Effects of Different Exogenous Substances on the Protein Conformation and in Vitro Digestion Characteristics of Low-salt Tilapia Surimi

The effects of glutamine transaminase (TGase), hydroxypropyl distarch phosphate (HDP), gellan gum and their complex (THG) on the water distribution and protein conformation of low-salt tilapia surimi gel prepared with microwave and ultrasound were analyzed. In addition, the effects of different exogenous substances on the characteristics of low-salt tilapia fish cake were explored through in vitro digestion experiment. The results showed that compared with the control group, THG increased the bound water and immovable water of surimi to 98.71% and 14.75%, respectively, and significantly decreased the free water content (P<0.05). Moreover, THG promoted the transformation of α-helix to β-folding, β-turning and random curling structures. TGase and THG (0.4%) played important roles on gastric emptying rate, protein digestibility and protein hydrolysis degree of low-salt tilapia cake. THG significantly promoted protein decomposition into aggregates with smaller particle size (P<0.05). After the digestion of stomach and duodenum, color of the THG group products was more transparent and clear. And it could be observed by the laser confocal microscope that the red fluorescence highlights of the THG group were significantly reduced, indicating that proteins had been fully digested. Hence, compared with a single exogenous substance, THG not only promoted the binding of water molecules and proteins and induced the change of protein conformation, but also facilitated the exposure of hydrophobic protein groups and the interaction between proteins, and promoted the digestion and absorption of surimi products in the stomach and duodenum. This project provided a theoretical reference for the research on the gel properties of tilapia surimi and the development and application of tilapia fish cake

Under-ice metabolism in a shallow lake in a cold and arid climate

Winter is a long period of the annual cycle of many lakes in the northern hemisphere. Low irradiance, ice, and snow cover cause poor light penetration into the water column of these lakes. Therefore, in northern lakes, respiration often exceeds primary production leading to low dissolved oxygen concentrations. This study aimed to quantify under-ice metabolic processes during winter in an arid zone lake with little snow cover. This study was carried out in a mid-latitude lake in Inner Mongolia, northern China. The study lake receives relatively high incoming solar radiation on the ice in mid-winter, and radiation can penetrate down to the bottom sediment as the lake is shallow and the ice lacks snow cover. Primary production and respiration were estimated during two winters using high-frequency sensor measurements of dissolved oxygen. To quantify under-ice metabolic processes, sensors were deployed to different depths. During both winters, sensors collected data every 10 min over several weeks. The amount of solar radiation controlled photosynthesis under ice; temperature and photosynthesis together appeared to control respiration. The balance between gross primary production and ecosystem respiration was especially sensitive to changes in snow cover, and the balance between P and R decreased. Our data suggest that photosynthesis by plankton, submerged plants, and epiphytic algae may continue over winter in shallow lakes in mid-latitudes when there is no snow cover on the ice, as may occur in arid climates. The continuation of photosynthesis under ice buffers against dissolved oxygen depletion and prevents consequent harmful ecosystem effects.Peer reviewe

Nondestructive testing of grating imperfections using grating-based X-ray phase-contrast imaging

We reported the usage of grating-based X-ray phase-contrast imaging in nondestructive testing of grating imperfections. It was found that electroplating flaws could be easily detected by conventional absorption signal, and in particular, we observed that the grating defects resulting from uneven ultraviolet exposure could be clearly discriminated with phase-contrast signal. The experimental results demonstrate that grating-based X-ray phase-contrast imaging, with a conventional low-brilliance X-ray source, a large field of view and a reasonable compact setup, which simultaneously yields phase- and attenuation-contrast signal of the sample, can be ready-to-use in fast nondestructive testing of various imperfections in gratings and other similar photoetching products.Comment: 6 pages, 5 figures and 2 table