Dynamic modeling of three-phase upflow fixed-bed reactor including pore diffusion

The dynamics of a three-phase upflow fixed-bed reactor are investigated using a non-isothermal heterogeneous model including gas–liquid and liquid–solid mass transfer and diffusion/reaction phenomena inside the catalyst. The partial differential and algebraic equations involving three integration variables (time and two space coordinates) are solved via discretization of the spatial coordinates coupled with the Gear method. For a multistep hydrogenation on a shell catalyst, the model exhibits significant effects of the external and above all internal resistance to hydrogen transfer but also non-trivial internal hydrocarbons concentration profiles. A simplified model is compared with the extended one and with experimental data in transient regime. In the investigated conditions—hydrocarbons in large excess—the diffusion of hydrocarbons appears to be actually not limiting, so that the simplest model predicts accurately the transient reactor behavior

Cross-linking of OX40 ligand, a member of the TNF/NGF cytokine family, induces proliferation and differentiation in murine splenic B cells

AbstractOX40 is a member of the TNF/NGF-receptor family expressed on activated T cells, whose ligand is found on activated T and B cells. In the present study, we show that cross-linking of OX40L on CD40L-stimulated B cells, αlgD dextran-stimulated B cells, or both results in a significantly enhanced proliferative response with no change In the cell survival rate. Furthermore, OX40 stimulation increases Immunoglobulin heavy chain mRNA levels and Immunoglobulin secretion, which could not be blocked by anti-cytokine antibodies. In additional molecular studies, we show that OX40L cross-linking results In the down-regulation of the transcription factor BSAP. This, In turn, leads to a change In the In vivo binding pattern of the imunoglobulin heavy chain gene 3′ α enhancer, suggesting its activation. This effect may thus be one mechanism for OX40-induced Increase In Immunoglobulin secretion. In conclusion, our data suggest that the OX40-OX40L interaction is a novel pathway in T cell-dependent B cell proliferation and differentiation

The role of two-stage phase formation for the solid-state runaway reaction in Al/Ni reactive multilayers

While extensively studied for heating rates below 1.7 K/s and above 1000 K/s, the solid-state phase transformations in Al/Ni reactive multilayers have not been examined at intermediate heating rates between 100 K/s and 1000 K/s. Combined nanocalorimetry and time-resolved synchrotron x-ray diffraction studies are utilized to address this range of heating rates for multilayers with an overall composition of 10 at. % Ni and a bilayer thickness of 220 nm. It was found that a two-stage phase formation of Al$_{3}$Ni proceeds up to a heating rate of 1000 K/s. The two growth stages occur in the solid-state and are kinetically separated. The activation energy of the first growth stage is determined to be 137 kJ/mol, which agrees well with the literature data at low heating rates. At 1000 K/s, a transition to a runaway reaction is observed. Unusual for metallic multilayers, the reaction proceeds completely in the solid-state which is also known as “solid flame.” Using nanocalorimetry, a critical input power density for ignition of 5.8 x 10$^{4}$ W/cm$^{3}$ was determined. The rapid succession of the two Al$_{3}$Ni formation stages was identified as the underlying mechanism for the self-sustaining reaction

Bias in Returns to Tenure When Firm Wages and Employment Comove: A Quantitative Assessment and Solution

It is well known that unless worker-firm match quality is controlled for, reduced-form estimates of returns to firm tenure will be biased. In this paper, we show that there is a further pervasive source of bias, namely, the comovement of firm employment and firm wages. We argue that firm-year fixed effects must be used to eliminate this bias. Estimates from two large-panel data sets from Germany and Portugal show that the bias is empirically important. Finally, we show that the results extend to tenure correlates used in macroeconomics, such as the minimum unemployment rate since joining the firm

Heterogeneous microstructures tuned in a high throughput architecture

A new method applied to the sensor proposed by Zhang et al. in 2018 is demonstrated in this paper that combines the benefits of this design with the fast heating possible with nanocalorimetry. By applying a PID regulated pulse instead of a constant wattage, we unlock an accessible method to sense morphological changes occurring over short time periods that would be invisible to methods based only on heat capacity. In this study, multilayer Ni/Al thin films were linearly heated at 25, 50, 100, and 200 K/s to over 700°C, showing two distinct peaks in resistance change with activation energies of 554 and 747 kJ/mol, respectively. Through Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive X-ray Analysis (EDX) analysis on cross sections taken ex situ from samples quenched before and after the peaks of interest, we find strong evidence that peak 1 corresponds to Ni diffusing through Al grain boundaries forming intermetallic phases that essentially block the highly conductive Al pathway. This presents the potential to design and calibrate novel heterogeneous structures in a high throughput manner

Cost and mortality prediction using polymerase chain reaction pathogen detection in sepsis: evidence from three observational trials

Delays in adequate antimicrobial treatment contribute to high cost and mortality in sepsis. Polymerase chain reaction (PCR) assays are used alongside conventional cultures to accelerate the identification of microorganisms. We analyze the impact on medical outcomes and healthcare costs if improved adequacy of antimicrobial therapy is achieved by providing immediate coverage after positive PCR reports