Experimental investigation of fuel-cooled combustor: Cooling efficiency and coke formation

Scramjet is an air-breathing engine designed to propel advanced aircrafts in the atmosphere, suitable, according to various studies, to thrust high-speed hypersonic flights (over Mach 5). The thermal protection of vehicles flying at hypersonic velocities is a critical problem; as at supersonic speeds the incoming air is at too high temperature to be used as a coolant, the fuel becomes the only adequate source of cooling for the vehicle. Regenerative cooling is a well-known cooling technique using the fuel as coolant. As the development of regeneratively cooled engines faces many difficulties, an empirical study of this cooling technology and of its complex dynamics is of high interest. In this context, a remotely controlled fuel-cooled combustor, suitable for the experimental analysis of the pyrolysis-combustion coupling characterizing a fuel-cooled combustion chamber when a hydrocarbon propellant is used, has been designed. Tests are realized under both stationary and transient conditions using ethylene as fuel and air as oxidizer. Two operating parameters, i.e. fuel mass flow rate (between 0.010 and 0.040 g.s-1) and equivalence ratio (between 1.0 and 1.5), have been investigated. It has been observed that fuel mass flow rate increases always result in the raise of the heat flux density passing from the combustion gases to the combustor walls. It has been seen that mass flow rate raises between 16 and 20 % lead to increases in the thermal energy evacuated by the fuel-coolant in the range from 30.4 to 48.5 %, depending on equivalence ratio and pressure. The dependence of the cooling system heat exchange efficiency on the two operating parameters has been demonstrated. The consequences of the coking activity of the fuel have also been investigated. For applied interest, a monitoring method for carbon deposits formation has been developed and validated

Magnetization Measurements on LHC Superconducting Strands

When using superconducting magnets in particle accelerators like the LHC, persistent currents in the superconductor often determine the field quality at injection, where the magnetic field is low. This paper describes magnetization measurements made on LHC cable strands at the Technical University of Vienna and the Institute of Physics of the Polish Academy of Sciences in collaboration with CERN. Measurements were performed at T=2K and T=4.2K on more than 50 strands of 7 different manufacturers with NbTi filament diameter between 5 and 7 micrometer. Two different measurement set-ups were used: vibrating sample magnetometer, with a sample length of about 8mm, and an integrating coil magnetometer, with sample length of about 1m. The two methods were compared by measuring the same sample. Low field evidence of proximity effect is discussed. Statistics like ratio of the width of the magnetization loop at 4.2K and 2K, and the initial slope dM/dB after cooldown are presented. Decrease of the magnetization with time, of the order of 2% per hour, was observed in some samples

The Tetraspanins CD9 and CD81 Regulate CD9P1-Induced Effects on Cell Migration

CD9P-1 is a cell surface protein with immunoglobulin domains and an unknown function that specifically associates with tetraspanins CD9 and CD81. Overexpression of CD9P-1 in HEK-293 cells induces dramatic changes in cell spreading and migration on various matrices. Experiments using time-lapse videomicroscopy revealed that CD9P-1 expression has led to higher cell motility on collagen I but lower motility on fibronectin through a β1-integrins dependent mechanism. On collagen I, the increase in cell motility induced by CD9P-1 expression was found to involve integrin α2β1 and CD9P-1 was observed to associate with this collagen receptor. The generation of CD9P-1 mutants demonstrated that the transmembrane and the cytoplasmic domains are necessary for inducing effects on cell motility. On the other hand, expression of tetraspanins CD9 or CD81 was shown to reverse the effects of CD9P-1 on cell motility on collagen I or fibronectin with a concomitant association with CD9P-1. Thus, the ratio of expression levels between CD9P-1 and its tetraspanin partners can regulate cell motility

New measurement of exotic decay of 225^{225}Ac by 14^{14}C emission

The branching ratio of $^{225}$Ac decay by emission of $^{14}$C was remeasured under improved experimental conditions by using a radioactive source produced at the ISOLDE mass-separator at CERN and a nuclear track detector technique. The result, B=$\lambda_{^{14}\textrm{C}} / \lambda_{\alpha} = (4.5 \pm 1.4) 10^{-12}$, is consistent with the anomalously high value obtained in the 1993 experiment thus confirming the importance of nuclear structure effects in this exotic decay

Low energy measurement of the 7Be(p,gamma)8B cross section

We have measured the cross section of the 7Be(p,gamma)8B reaction for E_cm = 185.8 keV, 134.7 keV and 111.7 keV using a radioactive 7Be target (132 mCi). Single and coincidence spectra of beta^+ and alpha particles from 8B and 8Be^* decay, respectively, were measured using a large acceptance spectrometer. The zero energy S factor inferred from these data is 18.5 +/- 2.4 eV b and a weighted mean value of 18.8 +/- 1.7 eV b (theoretical uncertainty included) is deduced when combining this value with our previous results at higher energies.Comment: Accepted for publication in Phys. Rev. Let

Recoil Proton Telescopes and Parallel Plate Avalanche Counters for the 235^{235}U(n,f) cross section measurement relative to H(n,n)H between 10 and 450 MeV neutron energy

With the aim of measuring the $^{235}$U(n,f) cross section at the n\_TOF facility at CERN over a wide neutron energy range, a detection system consisting of two fission detectors and three detectors for neutron flux determination was realized. The neutron flux detectors are Recoil Proton Telescopes (RPT), based on scintillators and solid state detectors, conceived to detect recoil protons from the neutron-proton elastic scattering reaction. This system, along with a fission chamber and an array of parallel plate avalanche counters for fission event detection, was installed for the measurement at the n\_TOF facility in 2018, at CERN. An overview of the performances of two RPTs - especially developed for this measurement - and of the parallel plate avalanche counters are described in this article. In particular, the characterization in terms of detection efficiency by Monte Carlo simulations and response to neutron beam, the study of the background, dead time correction and characterization of the samples, are reported. The results of the present investigation show that the performances of these detectors are suitable for accurate measurements of fission reaction cross sections in the range from 10 to 450~MeV

Chemical Imaging on Liver Steatosis Using Synchrotron Infrared and ToF-SIMS Microspectroscopies

Fatty liver or steatosis is a frequent histopathological change. It is a precursor for steatohepatitis that may progress to cirrhosis and in some cases to hepatocellular carcinoma. In this study we addressed the in situ composition and distribution of biochemical compounds on tissue sections of steatotic liver using both synchrotron FTIR (Fourier transform infrared) and ToF-SIMS (time of flight secondary ion mass spectrometry) microspectroscopies. FTIR is a vibrational spectroscopy that allows investigating the global biochemical composition and ToF-SIMS lead to identify molecular species in particular lipids. Synchrotron FTIR microspectroscopy demonstrated that bands linked to lipid contribution such as -CH3 and -CH2 as well as esters were highly intense in steatotic vesicles. Moreover, a careful analysis of the -CH2 symmetric and anti-symmetric stretching modes revealed a slight downward shift in spectra recorded inside steatotic vesicles when compared to spectra recorded outside, suggesting a different lipid environment inside the steatotic vesicles. ToF-SIMS analysis of such steatotic vesicles disclosed a selective enrichment in cholesterol as well as in diacylglycerol (DAG) species carrying long alkyl chains. Indeed, DAG C36 species were selectively localized inside the steatotic vesicles whereas DAG C30 species were detected mostly outside. Furthermore, FTIR detected a signal corresponding to olefin (C = C, 3000-3060 cm−1) and revealed a selective localization of unsaturated lipids inside the steatotic vesicles. ToF-SIMS analysis definitely demonstrated that DAG species C30, C32, C34 and C36 carrying at least one unsaturated alkyl chain were selectively concentrated into the steatotic vesicles. On the other hand, investigations performed on the non-steatotic part of the fatty livers have revealed important changes when compared to the normal liver. Although the non-steatotic regions of fatty livers exhibited normal histological aspect, IR spectra demonstrated an increase in the lipid content and ToF-SIMS detected small lipid droplets corresponding most likely to the first steps of lipid accretion